Xie Xide - the gentle president of China's Fudan University

At this very moment, China has more than 6,000 students studying in the United States at government expense. Most of them are in science and technology. That, to Dr. Xie Xide, president of Fudan University, is the most tangible proof that China's open-door policy toward the outside world is here to stay.

''It's quite an investment,'' said Dr. Xie of these students. ''They are the cream of our crop.''

Her own university, she said in a recent Monitor interview, has sent more than 300 students to the United States, of whom over 200 are now back working in China. Dr. Xie herself is what the Chinese call a ''returned student,'' having gotten her master's degree at Smith College and her doctorate in physics at the Massachusetts Institute of Technology. She was a part of the early post-World War II wave of Chinese students to the US - a group that included Nobel Prize-winners Yang Chenning and Lee Tsungdao.

Fudan, in Shanghai, is one of China's top universities, and to have a woman heading it is as unusual as having a woman head Harvard or Yale. Many Chinese ''take it for granted that I am a man,'' she said. Dr. Xie's first name, Xide, does not give away her sex.

Despite legal equality between men and women in China, ''people feel very strange when they find out I am a woman.''

Dr. Xie is also one of 210 full members of the Communist Party's Central Committee - the elite body that ratifies all major policies and chooses the country's top leadership. All the country's most powerful leaders, in the central government, in the armed forces, and in the provinces, sit on this committee. Dr. Xie's appointment to it in the fall of 1982 was taken as an indication of the Chinese leadership's commitment to honor intellectual achievement, particularly in science and technology.

Somehow, you forget all this when you meet her in person. In private life she is Mrs. Cao Tianqin, the wife of a distinguished biochemist and the mother of a promising young physicist now doing graduate work at the Chicago campus of the University of Illinois. And it is the caring quality, the rumpled tenderness that one associates with a wife or mother in a family of scholars that forms a visitor's first impression of Dr. Xie (Mrs. Cao).

She is small. Her feet barely touch the floor when she sits down on the sofa to which she has graciously waved her visitor. Her eyes are wide and disarming, her voice soft and unaffected. One could easily imagine her comforting a lonely freshman or encouraging a disheartened younger colleague.

''She has no enemies,'' said one of her admirers. And another added, ''She puts you at ease right away.''

But when Dr. Xie talks about her life, typical of that of many intellectuals of her generation, it is clear that here is a woman of backbone. The daughter of a physicist who taught at Yenching University (now part of Peking University), she fled from Peking with her parents soon after the Japanese occupied Peking in July 1937. After wandering across half of China, her family reached Guiyang okay. Pinyin spelling for Kweiyang in remote Guizhou okay. Pinyin spelling for Kweichow Province Province. Here she was ill and unable to move from her hospital bed for four years.

Eventually she recovered and attended Amoy University, where her father had found a teaching post and which had been evacuated to the hill town of Changding in Fukien Province to escape the Japanese.

Xide and her fellow-students greeted victory in 1945 with rapture. But they were soon disillusioned by the corruption of the Kuomintang, China's pre-communist government, and by the civil war that broke out between the Kuomintang and the Communists.

In 1947 Dr. Xie sailed on a GI troopship from Shanghai to take up a scholarship at Smith College and later went on to Massachusetts Institute of Technology. Meanwhile, the Korean war had broken out, and Chinese ''volunteers'' had fought American troops when they crossed the 38th parallel and advanced to the Yalu River.

Dr. Xie was determined to return to China, feeling that only there could she really be useful to her people. But in those days Washington was not allowing Chinese students to go home directly. Dr. Xie's fiance, Dr. Cao, had just completed his studies in Britain, and she decided to join him there. The two were married and returned to their homeland via the Suez Canal and Singapore in October 1952. Ever since, Dr. Xie has been at Fudan and her husband at the Shanghai branch of the Academy of Sciences.

Dr. Xie's faith in the new China was sorely tested when the Cultural Revolution broke out on Mao Tse-tung's orders in 1966. She was subjected to repeated sessions of criticism and self-criticism. For nine months she was incarcerated in a university laboratory with screaming Red Guards watching over her.

''Each day, I never knew what would happen to me,'' she said.

Her husband was undergoing the same treatment at his institute. Their son, then ten years old, had to fend for himself in a suddenly parentless apartment.

Later Dr. Xie was permitted to leave the laboratory to do menial tasks such as cleaning the hallways.

''Did you have to clean toilets?'' she was asked.

''Oh, yes, people liked to use my toilet,'' she replied whimsically. ''It was on the fifth floor, and I kept it very clean.''

There followed a number of years in the countryside, working in a factory making silicon wafers. In 1972 classes at Fudan resumed, and she was allowed to return to her teaching job. The students were all of worker, peasant, or soldier background, and their educational level was generally low.

''There were times when I felt almost hopeless,'' she remembers. ''Most of us survived - and some of us didn't. Today we can still laugh about our experiences when we look back.''

Dr. Xie had joined the Communist Party in 1956, at a time when it was encouraging intellectuals to apply for membership. She says she continued to keep her faith in the party throughout the Cultural Revolution.

''It was difficult,'' she acknowledged. ''We knew that what was going on shouldn't be party policy, and yet it was.''

Her faith was finally vindicated in October 1976, when the ''gang of four,'' headed by Mao Tse-tung's widow, Jiang Qing, spelling okay was arrested and the Cultural Revolution came to an end.

Since then, her major concern as a scholar and an educator has been to make up for time lost during ten years of chaos. She was appointed vice-president of the university in 1978 and president at the beginning of last year. The most pressing problem, she said, is to get good students. As one of China's top universities, Fudan has its pick of students.

''But to have better high schools, we need better middle schools and primary schools,'' she continued. ''It's all related. China is such a huge country, and teachers are still not fully qualified.''

There are now some 200 members of the faculty who have returned to Fudan from studies abroad, and Dr. Xie said they are already contributing to improvements in teaching and research. But she admits that it is not easy to find the specific job for which each returned scholar is most suited.

But if Dr. Xie has her frustrations, she keeps them to herself. Confronted with the impatience of younger colleagues, she reminds them that at China's stage of development, when the whole country is still striving to lift itself out of perennial poverty and attitudes dating from the feudal past, ''one needs more devotion to one's country than to one's own career.''

Through all the twists and turns of her own professional career, that is the motto she has lived by.

''After all,'' she said, ''do you not love your own mother, however poor she may be?''