The U.S. Commission on Civil Rights said yesterday that police brutality remains a serious problem in this country and is usually the trigger for urban disorders.

The commission called on Congress to give the Justice Department more power and staff to prosecute alleged misconduct cases.

Sharply criticizing Miami leaders, the commission also announced that it intends to hold hearings in coming months to determine the causes of the rioting there in May. The disorders were sparked by the acquittal of four policemen charaged in the beating death of a black Miami insurance salesman.

"We're going to try to find out whether the power structure [in Miami] has taken an interest in this," said commission Chairman Arthur S. Flemming.

"We feel that they've got to come out of those board rooms, out of those luncheon clubs."

The commission said in a preliminary report on "Police Practices and the Preservation of Civil Rights" that 19 years have passed since the group first took note of the problem. But commission members said in response to questions that it would be "cynical" to conclude that there had been no progress since then. Still, they said serious problems have persisted in cities such as Bringingham, Denver, Houston, Philadelphia, New York City, Memphis, Tampa and Wrightsville, Ga.

"Too often today, law and order means being shot or being killed by the police," said Mary F. Berry, vice chairman of the six-member commission. t

Justice Department officials estimate that in half a dozen cities police-community tensions may be as high as they were in Miami. As a result, the brutality topic has reappeared on the national agenda a dozen years after it was dealt with exhaustively in the Kerner Commission report on urban disorders.

The Law Enforcement Assistance Administration, which has been much criticized over the years for passing out millions to local police departments for armaments while giving insufficient attention to police misconduct, has in recent months allocated money for a new round of studies of the problem. h

The NAACP, the University of California at Irvine, the Urban League, the Police Foundation, and the International Association of Chiefs of Police have all embarked on new surveys with LEAA money.

The Community Relations Service of the Justice Department has established special offices in Miami and Houston in the wake of disorders.

And all around there is familiar talk of the need for more minority police officers, for tougher internal police department regulations on the use of deadly force, and for more outside review of police department decisions. These solutions were proposed before -- in the late 1960s.

Gilbert Pompa, director of the Community Relations Service, said that in some departments around the country little or nothing occurred in the way of reform over the last decade. In others, he said, police-commmunity relations units were formed and, for a while, their members had clout and were respected by fellow officers. But he said, by the end of the 1970s their role and resources were frequently reduced as traditional police fraternal organizations gained greater influence.

What has not changed, Pompa said, in the fact the police, in many cases the most visible symbols of authority in the ghetto, are still "on the first line of confrontation." Whether the root problems are lack of housing or jobs or decent education, complaints of police conduct most often give rise to disorders, he said.

In recent years, Pompa said, disorders have tended to be triggered not by incidents of alleged police abuse, as was the case in the 196os, but by acquittals of police officers charged with such misconduct.

This suggests that mistrust in urban communities now extends beyond police to prosecutors and the criminal justice system, Pompa believes.

"What you've got is a perceived feeling on the part of many that you've got to go directly to the [federal government] for relief," he said.

That was the thrust of the recommendations by the Civil Rights Commission in its preliminary report yesterday.

In addition to expanding the staffs of the community Relations Service and the Civil Rights Division in the Justice Department, the commission asked Congress to specify the federal government's authority to initiate suits against local police forces. It also called on the FBI to gather and report statistics on assaults and shootings by police.