CAMBRIDGE, Mass. (AP) _ About 5,000 Latin Americans who claim to have fled political persecution in their native countries have been quietly welcomed into this university city, and on Monday the City Council votes on whether to make the welcome a matter of public policy.

The council is due to vote on a proposal to declare Cambridge a sanctuary for illegal immigrants from Guatemala, El Salvador and Haiti.

''The purpose, fundamentally, is to have the city not participate in harassing undocumented aliens who are here for political reasons,'' said Alice Wolf, a city councilor who sponsored the sanctuary resolution. ''I believe we have an obligation to shelter people who are being persecuted in other countries.''

The proposed resolution states that agencies and employees of the city of Cambridge, ''to the extent legally possible,'' will not assist in federal investigations involving alleged violations of immigration law.

In addition, it says the city will not use lack of U.S. citizenship as grounds for withholding any services from Cambridge residents. Refugees may not be seeking medical treatment or sending their children to school out of fear of being deported, Ms. Wolf said.

In the past few years, about 200 churches and synagogues nationwide, including the Old Cambridge Baptist Church here, have declared themselves sanctuaries and opened their doors to Central American refugees.

In February, city councilors in Berkeley, Calif., declared that city a sanctuary.

Those involved in the sanctuary movement contend the Reagan administration is violating the Refugee Act of 1980 by deporting illegal aliens from Haiti and Central America, and that those who are deported face further persecution, torture and death. The federal act extends legal asylum to those fleeing political persecution or ''well-founded fear of persecution.''

The Reagan administration has refused to provide special status to the Central American refugees, arguing that most came to United States for economic reasons. Last month, the government's chief immigration official said the administration had been unable to confirm any widespread persecution of refugees who had been sent back to their native lands.

In December, the Immigration and Naturalization Service opened a detention center in Boston's North End.

Anne Shumway, a member of Refugee Alert, an organization that raises bail for refugees, said the action represented a stepping up of the government's campaign to root out aliens.

''We know that there is a real drive around the country to deport these people whose only crime is that they are trying to save their own lives,'' she said.

In Cambridge, a city of 98,000 that is home to Harvard University and the Massachusetts Institute of Technology, an estimated 3,000 Central Americans and at least 2,000 Haitians are living in fear of deportation, said Jeb Brugmann, director of the Cambridge Commission on Nuclear Disarmament and Peace Education.

One purpose of the Cambridge resolution, Ms. Wolf said, is to highlight the plight of the refugees so that the federal government will be forced to take seriously their request for political asylum.

The wording of the resolution, based on the one passed in Berkeley, has undergone scrutiny by city attorneys, but proponents acknowledge that its significance is largely symbolic.

''It's a humanitarian effort that when people flee war and come to Cambridge we are not going to cooperate in turning people back over to the governments from which they fled,'' said Nancy Ryan, director of the Cambridge Women's Commission.

''The city has a long tradition of people coming here to flee persecution,'' said Ms. Wolf. ''We must not turn our backs on those who follow.''