Thousands of Americans will descend on Washington Tuesday for President-elect Ronald Reagan's inauguration -- but not all of them will be here to celebrate.

Scattered bands of environmentalists, antinuclear activists, feminists, pacifists, anarchists, assorted Marxists and other radicals -- the traditional amalgam of American dissidents -- will also be here to register unhappiness with Reagan and his politics.

At least eight different groups totaling a few thousand demonstrators are scheduled to hold protest rallies at several sites near the White House on a wide range of political issues.

If there is one issue that binds these disparate groups, it is their contention that the Reagan election foreshadows an unhealthy shift to the right with an attendant emphasis on military and overseas expansion and de-emphasis on environmental and civil rights safeguards at home.

The planned actions mark the first sizeable inaugural protests since January 1973, when some 25,000 to 30,000 demonstrators rallied on the Washington Monument grounds against Richard M. Nixon. Police veterans grimly remember clashing four years earlier with militant antiwar demonstrators who attempted to disrupt Nixon's parade on Pennsylvania Avenue.

In contrast, at Jimmy Carter's inauguration in 1977, there was little protest action.

Police and Secret Service are now gearing up again for Tuesday, although officially they say they anticipate no problems. All days off and vacations have been canceled for the 3,680-member D.C. police force -- routine procedure for all inaugurations, officals say.

These and other precautions are taken not so much against demonstration groups as against a lone gunman or bomber along the parade route, they said.

The largest planned demonstration Tuesday will be a midday Peoples Counter-Inaugural march and rally from the Lincoln Memorial to the Ellipse, sponsored by a broad coalition of civil rights, prison reform, antinuclear and radical left organizers, including members of the Communist Workers Party.

Organizers say they expect 2,500 to 5,000 participants with bus loads coming from as far away as Florida and Ohio. Scheduled speakers at an afternoon rally on the Ellipse range from the Rev. Ben Chavis of the "Wilmington 10" and D. C. School Board member Frank Shaffer-Corona to Mario Valquez of El Salvador's Democratic Revolutionary Front and Andre Gaston, head of the Howard University student body.

More than a half mile away in Franklin Park, another crowd calling itself the Inaugural Project of the Immoral Majority, sponsored in part by the Youth International Party (Yippies) and other anarchistic splinter groups, plans an anti-Reagan rally that will include a mule-drawn wagon carrying a mock MX missile. Organizers have told police to expect up to 1,000 participants.

Authorities this year have also set aside a special demonstration area in Lafayette Square -- traditionally a favorite protest spot because of its nearness to the White House -- and at least five groups have already asked to use it. All small in number, they range from a band of Afghans protesting the Soviet invasion of their country to an antideath penalty group and an organization calling itself Marylanders United for Miscellaneous Causes.

Still another group called the John Brown Anti-Klan Committee says it will rally at the Justice Department on Pennsylvania Avenue. Police say a handful of participants is expected.