The Supreme Court settled the controversial issue of newspaper-broadcast combinations yesterday by voting 8 to 0to preserve most those in existence but to bar new ones.

The decision was a victory for the Federal Communications Commission, which is seeking to promote diversification of ownership in the mass media as a whole.

Upholding in their entirety regulations issued by the FCC in 1975, the court agreed with the commission that there must be divestiture in 16 "egregious cases" where, in relatively small communities, the combination includes the sole clear-signal television or radio station.

The decision leaves intact more than 140 combinations, many in major cities, in which the owner of a newspaper or of a communications chain is also the owner of a TV and/or an AM or FM radio station. The 16 divestitures, none of them in the District of Columbia, Maryland or Virginia, must be accomplished by Jan. 1, 1980.

The ruling reverses an order by the U.S. Court of Appeals for the District directing the FCC to adopt regulations to dissolve all existing combinations that would not qualify for waivers. But it upheld that part of the appeals court ruling that barred new combinations.

In the opinion for the cout, Justice Thurgood Marshall termed the FCC regulations "a reasonably means of promoting the public interest in diversified mass communications."

He rejected a claim by the appellate court that it was "arbitrary and capricious" to order divestiture in 16 cases while "grandfathering" existing combinations.

He also rejected objections by broadcasters and publishers, including a claim that barring newspaper owners from owning certain broadcast stations infringes on their rights under the First Amendment to the Constitution.

This argument "ignores the fundamental proposition" laid down by the court in a 1969 case that there is no "unabridgeable First Amendment right to broadcast comparable to the right of every individual to speak, write, or publish," Marshall said. Moreover, he said, "a newspaper need not forfeit anything in order to acquire a license for a station located in another community."

The decision drew varied reactions. The National Association of Broadcasters termed the decision upholding cross-ownership of media in the same market "gratifying." But owners in smaller markets who are being required to divest "are being treated unfairly," said NAB President Vincent T. Wasilewski.

Joe Dealey, president of the Dallas Morning News and chairman of an American Newspaper Publishers Association task force on cross-ownership, expressed a similar concern about the effect on those owners forced to divest.

Mark J. Meagher, president of The Washington Post Co., said he was pleased by the decision, "especially because it upholds the position the company took in the case."

Meagher added that the decision "will not affect the exchange of WTOP-TV in Washington with WWJ-TV in Detroit, which has been approved by the FCC and which will be consummated within the next few weeks."

Nicholas Johnson, chairman of the National Citizens Committee for Broadcasting, a nonprofit group that fought in the case to break up existing cross-ownerships, said the appellate court not the Supreme Court, was correct.

His group now is forced "back into guerrilla warfare" on a case-by-case basis, Johnson said. It will ask the commission to look first at Atlanta, where the Cox newspaper chain owns the morning and evening newspapers, a TV station, AM and FM stations and cable TV.

The Justice Department had argued that the FCC "did not propertly support" the crucial distinction drawn between approved existing combinations and disapproved new ones. But the appeals court "exceeded its authority" in purporting to decide, rather than to send back for reconsideration, unresolved questions about cross-ownership, the department said in its argument.

The FCC began in 1970 the rule-making proceeding that culminated in the 1975 rules. It "acted on the theory that diversification of mass media ownership serves the public interest by promoting diversity of program and service viewpoints, as well [as] by preventing undue concentration of economic power," Marshall wrote.

He pointed out that the FCC seeking to serve the "sometimes conflicting" goal of the "the best practicable service to the public," took into account factors such as the past broadcast record of an applicant for triennial license renewal and "a policy of avoiding undue disruption of existing service."

As a result, Marshall said, the FCC repeatedly has granted and renewed licenses held by newspapers "on findings that continuation of the service offered by the common owner would serve the ppublic interest."