The Philadelphia Bulletin, an institution here for nearly 135 years, will cease publication Friday, its owners announced today.

The Bulletin, once the largest evening paper in the nation, succumbed to mounting losses and plummeting circulation after a fruitless quest for a formula that would restore its preeminence or a buyer who would keep it going.

The paper's demise was like an instant replay of the death last August of the Washington Star, another venerable journalistic institution brought down by the nationwide flight of readers and advertisers away from big-city evening papers.

Executive Editor Craig Ammerman told the 1,900 employes at a newsroom meeting this morning that Friday's editions would be the last. He urged them to "go out with their heads high."

Publisher N. S. (Buddy) Hayden made the public announcement at a press conference. He said the Charter Co., a Jacksonville, Fla., conglomerate that bought the paper from the McLean family in April 1980 for $31 million, had failed to find a buyer and no longer could sustain its losses.

He read a press release quoting J. P. Smith, a Charter executive, as saying the paper lost $21.5 million in 1981 and now was losing $3 million a month. "The outlook for the rest of 1982 is equally bleak," he said.

The decision to close evidently was hastened by Charter's desire to write off the losses against its 1981 earnings, sources at the Bulletin said. Corporate tax rates for 1981 were higher than for 1982, and losses chargeable to last year therefore are preferable to a profitable parent company.

The end did not surprise Bulletin employes, who seemed more resigned than upset. The paper's troubles had been well-known for months, and Charter announced Jan. 7 that the Bulletin was for sale.

Hayden and Ammerman had told news department employes a week ago that the chances for saving the paper were poor.

"We knew it was coming," said Bill Hort, a photoengraver for 36 years. "We just couldn't get back the advertisers; you could see nothing was happening."

Hort is out of work with just three weeks' severance pay coming, though employes in other departments will get as much as 45 weeks.

Just over a month ago, Philadelphia had four daily newspapers. The sports-oriented Philadelphia Journal tabloid folded in December after four money-losing years. Now the city has only the morning Inquirer and the afternoon tabloid Daily News, both owned by the Knight-Ridder chain.

The Inquirer has been at work for months on a plan to expand if the Bulletin folded.

The Bulletin announced its own demise on its moving-lights news sign outside its plant and in a big front-page headline, "Bulletin to Close."

The plant, on Market Street at the Schuylkill River, is one of the most valuable pieces of real estate in Philadelphia, but there is no indication what Charter plans to do with it.

Inside, employes went through the now-familiar motions, cleaning out their desks, calling around to ask about jobs and giving interviews to reporters for surviving news organizations.

A sign at the personnel entrance announced unnecessarily "no applications currently being accepted." Delivery boys taunted departing employes, shouting, "You work for the Bulletin, and you don't have a job."

Security guards were posted to prevent the removal of company-owned equipment, just as they were last summer at the Star.

Rose DeWolf, the paper's irrepressible columnist, said there were few tears among the staff because the paper's demise long had seemed inevitable.

She said that staffers who could find other jobs began to leave months ago, and gallows humor took over the newsroom--as in the list of "101 Uses for a Dead Newspaper" that somebody had tacked to a post.

"The paper's dead but I'm not," DeWolf said as she was preparing a list of ideas for a New York literary agent.

Lee Rudakeywich, an editor who covered the war in Cambodia a decade ago, quipped that the subdued reaction of the staff was deceptive. "These Occidentals are good at masking their feelings," he said in a deadpan parody of a line often heard about the people of Indochina. He said he plans to collect unemployment insurance and write a novel.

In the 1940s the Bulletin had a circulation of more than 700,000, and it seemed to be an institution as durable as the statue of William Penn atop City Hall.

But the paper declined steadily throughout the 1970s under the conservative leadership of the McLeans--just as the family-owned Star declined in Washington. Last year the Bulletin's daily circulation dropped below 400,000.

Under Ammerman, the Bulletin tried all the usual methods of regaining lost prominence--new layout, more pictures, aggressive promotions and a morning edition. The only result was a steady progression of losses and a steady erosion of advertising.

Charter apparently did not seek joint production with the Inquirer under the Newspaper Preservation Act. Instead, it squeezed Bulletin employes for salary and benefit concessions, but a $4.9 million package surrendered by the unions last summer was not nearly enough to restore profitability.

Hayden said the decision to close became inevitable when negotiations with prospective buyers, whom he did not name, collapsed yesterday in New York.

"It obviously is sad to see a major newspaper with a proud lifetime of service to its community die," said Katharine Graham, Washington Post Co. chairman and American Newspaper Publishers Association president. "It's awful for the people who lose their jobs and for the community which loses a voice. But newspaper readership patterns are clearly changing. While the demise of a big-city daily attracts a lot of attention . . . I think it is important to note that newspapers today serve more communities than at any time in history."