Leonard Woodcock, president of the United Auto Workers, is the Carter administration's choice as envoy to the People's Republic of China, informed sources said yesterday.

Woodcock, 66, whose term as UAW president ends next months, was President Carter's special envoy to Vietnam in March. He won high marks from the State Department for his handling of the initial contact between the new administration and the Communist leaders in Hanoi.

Sources said Former Gov. Terry Sanford of North Carolina, an unsuccessful candidate for president last year, turned down an offer from the administration to be ambassador to France.

Sanford reportedly said he had promised to remain in his present job as president of Duke University after abandoning his bid for the White House last year. Though a moderate Southern governor like President Carter, Sanford was not an early or ardent Carter supporter.

Woodcock was a leading candidate to be Secretary of Health, Education and Welfare in the Carter administration but asked that his name be withdrawn from consideration for that job.

Like previous envoys to Peking, he will have the personal rank of ambassador, though the United States maintains a "liason office" in Peking, not an embassy. This is because the two countries have not yet established formal diplomatic relations.

The Peking post is currently held by Thomas S. Gates, 71, Secretary of Defense in the Eisenhower administration. Gates has been in China since May of last year.

Informed sources said that President Carter will also nominate Philip M. Kaiser to be ambassador to Hungary. Kaiser, 63, was ambassador to Senegal in the Kennedy administration and minister to the Court of St. James's under President Johnson. He was assistant secretary of labor for international aff