United Nations Ambassador Jeane Kirkpatrick, addressing more than 500 graduates at Georgetown University's 182nd annual commencement, yesterday reminded them to "worship God, family life, seek justice and honor truth."

Kirkpatrick said she had consulted friends about her speech and received three pieces of advice -- "make it brief," "make it funny" and "don't talk about foreign policy" -- all of which she accomplished to the delight of the graduates, who roared with laughter in response to her decision, hoisting mortarboards and magnums of champagne in festive approval.

The students, who doused themselves with the traditional champagne as each major division was called for its degree, interrupted her several times with friendly applause.

However, there was some muted hissing and booing as Kirkpatrick, a Georgetown professor for 10 years before taking leave to accept the U.N. post, received an honorary degree.

When she spoke to students at the University of Pittsburgh last month, 45 students turned their backs to her in protest of Reagan administration policy in El Salvador and South Africa. On April 16 the ambassador withdrew her acceptance of an invitation to address graduates at Trinity College here after similar opposition was voiced by students and faculty.

Focusing on the students and faculty, "her family" at Georgetown, she said that the culture of Western civilization and Christian tradition have conferred upon them the kind of freedom "about which the Greeks never dreamed." She briefly acknowledged the controversy over her choice as speaker, but said that her years of teaching have made her and the school inseparable.

"In the past 10 years I estimate I have graded at least 10,000 papers here. . . . Georgetown University has become a part of me, it is an identity I cherish," she said.

The choice of Kirkpatrick to give the main address was not officially announced by the school until yesterday, following a decision by university president Timothy S. Healy two months ago to keep the speaker's identity closely held until the day of commencement to create surprise and allow flexibility in the choice. President Reagan, currently vacationing on his ranch in California, was the school's first choice but he declined.

A university official acknowledged privately that the policy over the speaker was also aimed at muting possible protest demonstrations at the ceremonies.

"If you don't announce it, you won't have half the world organized to protest something, like El Salvadorl," said the official. "Any government official is a lightning rod for protest," the official added.

About two dozen black robed graduates wearing white armbands either stood and turned their backs to Kirkpatrick as she spoke, or turned their chairs away from the podium. From outside the gates of Copley Lawn where the ceremonies were held, about 30 placard-carrying demonstrators could be heard chanting, "Georgetown students turn your backs . . . . ." during the speech.