Why in the early 1970s, the chinese government decided to improve relations with the u. s.?

The U.S was no longer directly involved in conflicts against communist forces in South-East Asia. In addition to this were border disputes between the Chinese and Soviet Union. The bigger threat to China now appeared to be the Soviet Union, not the USA. At that time, the cold war was entering a period of detente in which relationships between the US and Communist powers changed. China stood to benefit from improving relations. China needed export markets for her industrial goods and improved relations with the US would enable this. Therefore, They agreed to cooperate to build a good relationship so that they could export products into the U.S.