Kevin H. White, one of the nation's most resilient, dynamic and--recently--embattled big city mayors, tonight announced to a public primed to hear something entirely different that he will not seek a record fifth term.

"There does come a time in the life of every man and any city when change is appropriate," White, 53, said in a five-minute speech that he taped Wednesday in New York under extraordinary secrecy.

He then had the tape delivered by top aides, who had a police escort, to three local television stations minutes before they were broadcast in a paid commercial spot at 6:55 p.m.

Such was the furtiveness and disinformation surrounding the announcement, which this city's tabloid newspaper--The Boston Herald, which is owned by publisher Rupert Murdoch--announced in a headline appropriate in size to the outbreak of World War III.

It blared, incorrectly: "White Will Run" on the front page of its editions all day.

White's City Hall communications staff, as much in the dark as anyone, even had an office pool on the announcement.

"It's like who shot J.R.," said city councilor and mayoral hopeful Raymond Flynn.

With the announcement, White, the son and grandson of prominent city politicians, brings to a close a 16-year tenure that won him high praise for his stewardship of the renovation of the city's downtown, but also brought mounting criticism that he presided over a City Hall riddled with corruption and excessive patronage.

White never has been indicted, but in the past three years six middle-to-high-level city officials have been convicted of a variety of corruption charges stemming from investigations by the FBI, the Internal Revenue Service, the U.S. attorney and the Department of Housing and Urban Development.

White long has maintained that the corruption probes were politically motivated.

His retirement leaves a wide open field for the 10 announced candidates--six of whom are considered serious contenders--in the nonpartisan mayoral primary in September.

Although a number of the candidates are former political allies of White, all have been unsparing in their criticism of the snow-white-haired figure known as "King Kevin." There is no candidate from the so-called "White machine" in the race.

White's decision in 1976 to build a political machine, which many observors here believe contributed to his undoing, stands as the most dramatic tactical decision of his tenure and provides a point of demarcation for what many here consider the "two" Kevin Whites.

"Kevin White is a big city mayor trying to accomplish John Lindsay's goals with Richard Daley's methods," Rep. Barney Frank (D-Mass.) recently said of the man for whom he once worked.

White was elected in 1967 as a street-savvy and media-savvy reformer, determined to open local government to non-traditional constituencies such as blacks, Jews and Italians. He promised to recruit top experts and to depoliticize city services by opening "little city halls" in ethnic neighborhoods.

In the early years, his star was ascending, its glow barely dimmed by his defeat in a 1970 race for governor.

He was the tough-talking but urbane Irish pol who had the reputation of taking on Louise Day Hicks on the explosive school busing issue and bringing a provincial New England city kicking and screaming into the 20th Century.

There was talk of him as a future national candidate, and he apparently came within hours of being selected as George McGovern's running mate in 1972 until, according to local lore, Sen. Edward M. Kennedy (D-Mass.) blocked him.

White's 1975 reelection campaign was bitter. He was under fire on charges of corruption, and his position on school busing--he opposed the court-ordered plan but he was determined to enforce the law--won him few friends.

After winning the close 1975 race, White decided to build a machine to buttress his administration against the whims of public opinion. He appointed ward coordinators and precinct captains, and citizens with routine needs were encouraged to work through them. The little city halls were closed.

Even as the city continued to blossom--in his upbeat speech White spoke tonight of Boston as a high-tech capital of the world, its Fanieul Hall and Quincy Market development projects as national models of urban renewal--City Hall began to take on stench of patronage and corruption.