A major exhibition of American art will tour the People's Republic of China in 1981. It is the first official exhibition to go to China since the two countries broke off diplomatic relations 30 years ago. The announcement was made by yesterday by the U.S. International Communication Agency.

Seventy as-yet-unselected paintings, all from the Boston Museum of Fine Arts, will survey 250 years of American art history, from colonial times to the present. The exhibition is a result of the 1979 U.S. China Cultural Agreement, signed just after normalization of relations. The agreement also provides for an exhibition of Chinese art in this country, though no definite plans have yet been made.

The Boston-China connection dates back to the 18th-century maritime trade between the two. In the past year, the Boston Symphony Orchestra became the first American orchestra to perform in China since normalization. That tour was supported in part by a USICA grant. The Boston Ballet, under private auspices, also visited China last year.

USICA, which is responsible for administering the cultural agreement for the United States, is also cooperating with the Chinese Ministry of Culture on other exchanges, including a forthcoming U.S. film festival in China in 1981, to be followed by a Chinese film festival here. The Voice of America, USICA's international radio service, and Radio Peking are also involved in an exchange-of-persons program.

John Reinhardt, USICA director is currently in China as head of a U.S. cultural delegation that includes National Endowment for the Arts Chairman Livingston Biddle Jr., National Endowment for the Humanities Assistant Chairman Thomas Litzenberg, Kennedy Center Artistic Director Marta Istomin, Smithsonian Assistant Secretary Julian Euell and National Gallery of Art senior curator John Wilmerding. They will leave China on Monday.