ONE OF THE MOST important events of our times is the decision by leaders of the People's Republic of China to resume economic intercourse and expand contacts of all kinds with the outside world, including the Western capitalist states.

Chairman Hua Kuo-feng's state visits to Romania, Yugoslavia and Iran have been heralded as a symbol of the new openness. Less dramatic, but equally important, are the overtures to the United States, Japan and some Western European countries to undertake joint economic ventures.

"They have come to realize that they can't even begin to realize their targets for industrialization by the end of the century if they try to do it all by themselves," says Christopher Phillips of the Washington-based National Council for U.S. China Trade.

Chou En-lai had set as a goal for China the creation of "the most powerful Socialist state by the year 2000." But it has taken pragmatic decisions by Hua and his deputy, Teng Hsiao-ping, to make Chou's open challenge to the Soviet Union more than rhetoric.

To sympathetic Westerners, Teng has expressed the new policy in this simple way. "It doesn't matter whether the cat is black or white. What matters is whether it gets the mouse."

With that as a guideline, China's new leaders, putting ideological hangups behind, are out to get what help they can from the West in oil, steel coal development, computers, fertilizers - to name just a few industries where Western companies have been approached.

WESTERN NEEDS for energy and China's enormous oil resources have provided a convenient bridge. Early this year, Energy Secretary James Schlesinger gave red-carpet treatment to a high-level Chinese delegation here to discuss American participation in exploring for oil in the China seas.

The Peoples' Republic then seized the initiative, inviting four major U.S. companies to make proposals for seeking and developing oil. Industry officials, who responded promptly to the opportunity offered, believe that the Chinese are looking not merely for technical aid, but are willing to let U.S. and other companies acquire some of the oil.

For the West, it is another sign that the supposed "lock" that the Middle East has on future oil supplies is not so tight. In 1973, when the Organization of Petroleum Exporting Countries boosted prices four-fold, who could have anticipated the Mexican oil bonanza? Now there is China, with vast untapped reserves. Who knows what next?

For China, the sale of oil - which in time could be very substantial - will provide the cash it needs to buy equipment and technology of all kinds.

The abandonment of the old Chinese xenophobia has been exhibited in many other ways. Chinese journalists are exploring other parts of the world. An increasing tourist trade in China is welcomed. In another area, education, big things are happening. For the past 10 years, there are been an education "gap" during which few managers, technicians and specialists were churned out.

"Young people got into school if they were strong on the right ideology - there were no real entrance exams," an official here explains. This gap did serious damage to China's economic growth potential. And there are little opportunity for the Chinese intelligentsia to make contact with their opposite numbers elsewhere.

Now, all this is changed. Hua and Teng are seeking brains, not affirmation of political dogma. And as part of the effort to get out of the West whatever the West will give, thousands of students are being sent out to soak up expertise and bring it back home.

THE AMERICAN REACTION throughout the Carter administration has been positive. It is giving moral support to the National Council as a vehicle for stimulating trade. The oil companies are being encouraged to make their deals with China, and Schlesinger is going to Peking next month to see what he can do to help the process along.

Beyond that, Carter's science adviser, Frank Press, recently led a team of seven U.S. agencies that established good rapport with their opposite numbers in Peking. This effort has been supplemented by a private Committee for Scholarly Communication with the PRC which has opened lines of contact with scientists, teachers and members of other professions.

One doesn't have to expect the overnight delivery of thousands of tons of oil to believe that we are at the threshold of a new era. China has the potential to become one of the two or three leading economic powers of the world. If developed fully, China not only could provide a significantly higher standard of living for its millions, but would have the capacity to aid millions of less fortunate people, especially in Asia. A smoother and growing relationship with the United States and the PRC is bound to accelerate the timetable.