Members of the graduating class at Stanford University have planned a mass walkout for the middle of their commencement ceremony Sunday to protest the appearance of Daniel P. Moynihan, professor of Government and ambassador-designate to the United Nations, student and administration sources said yesterday.

The protestors have attempted to cancel Moynihan's appearance since its announcement in April, citing what they called his racist position regarding the welfare of blacks that he assumed as a domestic adviser to former President Richard M. Nixon.

Leaders of the planned demonstration were unavailable for comment yesterday, but Daniel J. Fiduccia, a reporter for The Stanford Daily who has covered the protests since the speaker committee's choice was announced, said that it is not clear how many people will leave the ceremony when Moynihan is introduced.

Robert M. Rozenzweigh, Stanford's vice president for university relations, said yesterday that he was aware that some seniors plan to walk out, but he said "it will probably be a small number."

"We don't expect a serious problem--people have the right to walk out, and we assume that they will do so in a quiet dignified fashion," he said.

Rosenzweig said that members of the administration at Stanford have informed Moynihan of the planned protest.

Moynihan was unavailable for comment yesterday.

Graduating seniors who object to Moynihan attempted last month to arrange to conduct an alternative graduation ceremony, but Stanford refused to allow them to have a separate diploma-awarding ceremony, Fiduccia said.

"Many of those who don't think Moynihan's a racist and an imperialist feel he's a boring, uninteresting speaker," Fiduccia said, adding that many Stanford seniors are unhappy with the selection process used to find speakers for the June 15 commencement.

Moynihan was the Stanford speaker committee's fourth choice, after Katherine S. Graham, Shirley Hoffsteader and Robert Penn Warren declined invitations to speak