Mainland China puts its hand to writing peace treaties

''DEAL with it before it happens. Set things in order before there is confusion. . . .'' These words, from the ancient Chinese philosopher Lao-tzu, capture the challenge of maintaining - indeed, waging - peace. President Reagan's active search for peace has just taken him to China, a great and vital country certain to play a larger international role in the future. The President's agenda in Beijing (Peking) was rich with topics, and arms control was among them.

The Chinese have, over the centuries, broken new ground in many fields - including their study of strategy. The great and revered military theorist Sun-tzu, writing in the 6th century BC, emphasized the achievement of victory without warfare. Yet, until recently, the Chinese have not been active participants in international arms-control activities.

Today China is more creatively engaged in international politics, where arms control is a key component. In a few short years China has signed three major arms-control treaties: the Antarctic Treaty, the Outer Space Treaty, and the Treaty of Tlatelolco. The first ensures that the vast continent of Antarctica will be used for peaceful, not military, purposes. The second prohibits, among other things, putting any weapons of mass destruction in outer space. The third is designed to establish a nuclear-free zone in Latin America.

China now actively participates in the 40-nation Conference on Disarmament in Geneva, where Vice-President George Bush has just presented the US draft treaty for a total global ban on chemical weapons. In a new initiative China put forward detailed proposals of its own for a chemical-weapons ban. Our objectives in this area have common foundations.

The Chinese have also taken a number of steps in the area of nuclear nonproliferation. While they remain critical of the Non-Proliferation Treaty (they consider it discriminatory), they have signaled that they share the worldwide concern that the further spread of nuclear explosives represents a threat to mankind.

In particular, this year China joined the International Atomic Energy Agency - the world body that, among other things, helps to ensure that peaceful nuclear activities (such as nuclear power plants, research reactors, etc.) are not used for military or nuclear explosive efforts. Second, Chinese Premier Zhao Ziyang stated during his January visit to the United States that China will not ''encourage nuclear proliferation'' or ''help other countries develop nuclear explosives.'' Third, China has indicated that it will require international safeguards on its nuclear exports.

Finally, as announced in Beijing, the US and China have reached agreement for cooperation in peaceful uses of nuclear energy. This is comparable to the agreements between the US and other countries. It provides for cooperation in the development of nuclear power under agreed procedures and controls, which contribute positively to the achievement of our nonproliferation objectives.

These moves on arms control have to be viewed in the broader scheme of things. The Chinese keep a wary eye on the Soviet military buildup in the Far East, which outpaces the more publicized expansion in Europe. With its neighbors in the Pacific, China has watched with concern as the Soviets have expanded their Pacific Fleet; strengthened their 52 tank and motorized rifle divisions in the Far East; and deployed 135 of the new triple-warheaded SS-20s in the eastern USSR. Nor is China oblivious to what is happening in neighboring Afghanistan. The Chinese have followed closely the US-Soviet nuclear-arms-control negotiations and the international controversy over the use of chemical weapons in Afghanistan and Southeast Asia.

We welcome and encourage a more active Chinese role on arms control but we need to be realistic in our expectations. China will move cautiously and avoid becoming entangled in ''superpower'' issues in ways that would impair its independent stance in international affairs. Yet the world community should recognize the slow but steady Chinese awakening to the possibilities and promise of arms control. As President Reagan said in Beijing's Great Hall of the People, ''Our countries share the same basic principles of preserving world peace and preventing the destabilizing spread of nuclear explosives.''