The Maryland State Police agency has attained a longstanding court-ordered goal of 14 percent black membership in the 1,548-member force after an intense recruitment and advertising effort in black communities, Superintendent George Brosan announced today.

After years of racial antagonism and allegations of manipulated promotion test scores for favored officers in the upper ranks, Brosan said he is on the way to abolishing discrimination and what he called a "terrible system" of politically tinged old-boy favoritism.

The goal of raising the number of blacks to 14 percent of the State Police force dates to 1974 when the agency, in a racial discrimination dispute with the Justice Department, accepted a federal court consent decree.

Brosan, a former federal drug enforcement official and political outsider brought in last November by Gov. Harry Hughes to revamp the troubled agency, said today that 43 of the 228 promotions in the agency since he took over have gone to blacks.

There are now four black lieutenants, he said, including for the first time a barracks commander. Also for the first time, he said, two black troopers have been sent to so-called executive career development schools, one at the Northwestern University Traffic Institute in Evanston, Ill., the other at the FBI academy in Quantico, Va.

"The level of racial antagonism has gone down," Brosan said. "I'd be foolish to say it doesn't still exist in some dark corner of the Maryland State Police. But generally I think the atmosphere is much improved."

Cpl. Larry Schuyler, president of the Coalition of Black Maryland State Troopers, agreed that "some problems have been alleviated . . . but they have not been totally resolved."

He said his organization would like to see the proportion of black troopers determined eligible for promotion at the barracks level for corporal and sergeant raised between 33 and 50 percent.

Brosan, former chief of Maryland operations for the federal Drug Enforcement Administration, said he has implemented an improved interim promotion plan after an investigation last year by the office of Maryland Attorney General Stephen H. Sachs found promotion favoritism and other irregularities in the agency's upper ranks.

Several high officials resigned and Col. Wilbert T. Travers Jr. retired as superintendent after Sachs' office accused him of doing little to eliminate promotion irregularities reported as far back as 1982.

Brosan said a permanent new promotion system is being designed by Morris & McDaniel Inc., an Alexandria industrial psychology consulting firm.