Nearly two months after the fatal shooting of Sean Bell, support for the Police Department has plummeted and Mayor Bloomberg’s approval rating matches his highest rating ever, a study released yesterday shows.

The Quinnipiac University poll found that 75% of voters approve of the job Mr. Bloomberg is doing. By contrast, the police commissioner, Raymond Kelly, received a 52% approval rating, down from 70% in February.

Overall, 53% of those polled said they approved of the job police are doing, compared with 72% in April. Among black voters, 68% said they disapprove of the work by police.

The poll also compared the current administration’s approval ratings to those of Mayor Giuliani and Commissioner Howard Safir in April 1999, two months after the shooting of Amadou Diallo. At that time, Mr. Giuliani’s approval rating was 40% and Mr. Safir’s was 38%.

Generally, analysts said they were not surprised by the poll’s results. “The shooting had profound reverberations in the black community,” a professor at the School of Public Affairs at Baruch College, Douglas Muzzio, said.

Last night, Mr. Kelly discussed the Bell case and yesterday’s poll results on NY1’s “Inside City Hall.” Conceding he expected that fewer people would have been concerned about overall police misconduct, he said: “Everybody is not going to be happy with police.”

Pollsters reported that 68% of respondents believe police brutality is a “very serious” or “somewhat serious” problem.

Meanwhile, political analysts offered several explanations for Mr. Bloomberg’s ratings, including the mayor’s initial assessment of the Bell shooting — that it seemed as if police had used “excessive force.” Bell was shot in a hail of 50 bullets on November 25 outside the Kalua Cabaret in Jamaica, Queens.

A Democratic political consultant, Bill Lynch, praised Mr. Bloomberg for meeting with black leaders and elected officials after the shooting. “If you go back and look through his record, Mayor Giuliani was criticized for not reaching out after the Diallo shooting,” Mr. Lynch said.

Some said Mr. Giuliani’s approval ratings slipped after the Diallo shooting because of his close ties to the Police Department.

“Giuliani, for better and worse, linked himself so much with the Police Department that it’s no surprise” his ratings declined, a former police officer who is a professor at John Jay College of Criminal Justice, Peter Moskos, said.

A spokesman for the mayor declined to comment on the poll.

The telephone survey of 1,013 registered city voters was conducted in the second week of January.