Montgomery County Executive Charles W. Gilchrist has chosen Bernard D. Crooke Jr., second in command of the District of Columbia Police Department, to be the county's new policy chief.

If his appointment is approved by the County Council, Crooke would replace controversial police chief Robert J. diGrazia, whom Gilchrist fired in December.

In selecting a successor to diGrazia, Gilchrist said he wanted a chief who would continue to move away from traditional concepts of law enforcement without provoking antagonism among his officers as the flamboyant diGrazia did.

A 23-year police veteran, Crooke has held numerous positions in the D.C. force, ranging from patrolman to detective, district commander and head of the department's planning and development division.

Crooke, 45, has been an assistant chief in charge of field operations in the D.C. department since January 1978, in which job he supervises the day-to-day operations of the department from homicide investigations to hostage situations.

His salary is now $47,500. They salary of the Montogmery County police chief is currently $52,811. If Crooke retires from the D.C. department before moving to Montgomery, he would be entitled to receive a pension that would bring his annual income to about $80,000.

Crooke a Washington native who has lived most of his life in Montgomery County, would neither confirm nor deny yesterday that he is Gilchrist's choice. "I'm interested in the job," he said. "I have a very high regard for the Montgomery County Police Department. I have always been impressed with the Montgomery department.And I have many friends [in the department] whom I met as an investigator and whose friendship I still maintain," Crooke said.

Gilchrist confirmed he had made a selection but refused to reveal the name. He said, "We still have some-people to talk to" and some details to work out.

The son of a retired District homicide detective, Crooke is described as a progressive thinker who supports the extensive use of civilians in police departments and the concept of citizen advisory councils.

He formed the District's first store-front community center where citizens could go to talk to police officers in an inner-city neighborhood in 1975.

Crooke has also maintained a high level of respect and loyalty from the D.C. force's rank and file. That aspect is important since Gilchrist fired diGrazia because he said he believed diGrazia's strained relationship with his officers had rendered him ineffective in leading the department.

Crooke has been widely considered as a possible successor to D.C. Police Chief Burtell Jefferson, who was appointed in 1977. However, many department sources haye said that in the political atmostphere of the District, Crooke, who is white, has little chance of becoming chief. Mayor Marion Barry has said that a predominantly black city such as Washington should have a black police chief.

Maj. Donald E. Brooks, a reserved man who comes from the old school of policing has been running the department since diGrazia's dismissal last December. Brooks, a 28-year veteran of the force, took the job intending to retire at the end of six months, but recently expressed interest in remaining on as chief since he said he had helped improve police morale.

Brooks said last night he "planned all along to retire."

Maj. Wayne Brown, the seecond in command in the Montgomery department, said he knows Crooke and that Crooke was a "top-rate detective." Brown, who said he has been considering retiring from the Montgomery force, noted that "The troops thought [crooke] was a good choice when he was appointed deputy chief [in] Washingron. That means a lot if the rank and file appreciate him."

But the presidents of the Police Association and the Fraternal Order of Police issued joint statement to Gilchrist saying that they were "disap pointed" that their organizations did not have an opportunity to participate in the selection process.

They urged Gilchrist to defer selecting a permanent chief until Brooks' administration "is allowed a reasonable time to demonstrate its effectiveness."

Officer Robert McKenna, president of the Police Association, said Gilchrist had told officers while he was campaigning he "would like to promote (a police chief) from within (the department)."

Officer Rick Nelson said he did not think Montgomery's rank and file would be disappointed that an outsider was selected because Crooke has a good reputation in the area as an officer with "an enormous amount of practical police experience. He's not a textbook policeman."

During Cooke's 30-month term as commander of the 3rd District polcie station, which takes in an area around 14th and U streets NW where narcotics and prostitution are serious problems, crime was reduced in the area at a time when crime citywide was increasing.

One of Crooke's acts was to set up the 3rd District's first citizen advisory council.

"I think (Crooke) is probably one of the best officials we've ever had," said Officer Robert Jenkins of the 3rd District, a past president of the Afro-American police association.

"He would not only listen to you, but evaluate what you told him and do something about it... Some police officials will back another official on a decision concerning a patrolman whether it be right or not. But not Chief Crooke. If he thought that the official was wrong and the patrolman right, he'd call the official in and straighten things out."

When diGrazia was picked to be Montgomery's chief in November 1976, there was a national search for candidates.

In contrast, the selection process for deGrazia's successor was shrouded in secrecy. County sources said Gilchrist made the decision in conjunction with his chief administrative officer, Robert Wilson.

The job was never advertised, but there were 30 applicants. Among those considered were Brooks, Chief Charles Wall of the Rockville Police Department, Chief John Rhodes of Prince George's County and retired D.C. Police Chief Maurice Cullinane.

Gilchrist told a close friend he thought Brooks had done a good job, but he wanted to bring in someone from the outside.

According to sources, Gilchrist wanted a chief who would keep the department out of controversy after the tumultuous two-year diGrazia administration.

During that time, diGrazia reorganized the department to eliminate some top administrative positions, put more sergeants on patrol and streesed community relations, more extensive and sophisticated training and the use of civilians and outside consultants to help form policy.

DiGrazia, whose national reputation as an outspoken, innovative police chief in Boston and St. Louis County preceded him in Montgomery, had a flamboyant, oratorical manner that eventually cost him his job.

What triggered his firing was a statement at a public forum in November that most police officers "view the community as the enemy." But before that time, a majority of the Montgomery chapter of the Fraternal Order of Police had voted no confidence in him.

DiGrazia is now appealing his firing to the Maryland Court of Special Appeals and is suing the county for $6.5 million, contending his firing diminished his future employment prospects.