The congregation that filed into Elijah United Methodist Church in Poolesville yesterday already had heard the news: Vandals had broken into their church, tearing down the drapes, stealing the American flag and carving the oak communion table with three letters: KKK.

It was not the first time that blacks in Poolesville have had to confront racial hatred. Through the years, many residents have found racial epithets written in crayon and spray paint scrawled across their screen porch windows and driveways. Tensions between blacks and whites in this rural Montgomery County town date at least to the 1960s, when integration of the local schools was resisted. Previously, blacks in Poolesville were bused to schools in Rockville.

But this was the first time a church had been defaced in Poolesville. News of the incident was spread by telephone throughout the church community.

During her sermon yesterday, the church's minister, the Rev. Miriam H. Jackson, stood before the small oak table that had been carved with the letters KKK. "We will not allow ourselves to be destroyed by these acts of terror and violence," she said. "We will not fight evil with evil; we will not fight violence with violence."

The vandalism was discovered Saturday by church member Doris Lyles. Lyles immediately phoned Jackson, who drove to the church, walked down the aisle and stood before the communion table where she saw the three-inch high letters: KKK. "I cried 'Oh God,' " Jackson said during her sermon yesterday.

The hate messages found in the small frame church are part of a continuing problem of racial harassment in Maryland. Between July and the end of December 1981, 385 incidents of racial hatred were reported to the Maryland Commission of Human Relations through local police, said JoAnne Evans-Anderson, director of community relations for the group.

Montgomery County reported 72 incidents, the highest of any county in Maryland. Baltimore County followed, with 63 reported incidents.

The hate incidents have become so numerous that Montgomery County delegate Luiz Simmons last month introduced a bill in Annapolis that would provide jail terms and stiff fines for anyone distributing literature that "holds the citizens of any race, color, creed or religion up to public contempt, shame or disgrace." His bill has not been acted upon.

County police said they have not arrested anyone in connection with the church vandalism.

The congregation normally numbers 30, but news of the incident swelled attendance to about 100 men and women yesterday. Many were community leaders and members of other churches who came to express support for the congregation.

Roscoe Nix, the head of the Montgomery County chapter of the NAACP, stood up immediately after the sermon and spoke. "I am here to show you you have friends," Nix said. "The persons who are really desecrated are the perpetrators of this act."

Then, one by one, men and women stood up in the church and spoke against the vandals. Tom Starnes, a district superintendent for the church, expressed his sorrow that the congregation had been "reminded of the hate in the minds and hearts of some people."

Alan Dean of the Montgomery County Human Relations Commission said he wanted to show the congregation "what love is and what support is."

Another who stood was Lincoln Dring, director of the Montgomery County Community Ministry. He said his organization would "help you in any financial burden you have to carry because of this action."

After the service, men and women walked to the altar and viewed the damage. Someone suggested that the rudely carved letters be emblazoned in gold, but Pastor Jackson rejected that as "unnecessary."

"Mr. Pruitt, the shop teacher at the Poolesville High school, has offered to refinish the table," she said. "I think that's a very good idea."