Joseph Christopher, a 26-year-old white Army private, was convicted yesterday of slaying three blacks in Buffalo with a sawed-off .22-cal. rifle in September, 1980.

Christopher showed no emotion as the verdict was read at his nonjury trial.

The slayings terrorized the black community in this industrial city on Lake Erie. Prosecutors portrayed Christopher as a man who hated blacks and killed his victims simply because of their race.

The guilty verdict, on three counts of second-degree murder, drew cheers from a crowd outside the courtroom and praise from black leaders.

Mayor James Griffin, who is white, said, "It's great for the community to know that justice has been served."

Christopher will be sentenced May 24.

He was accused of murdering a black youth and three black men in a 30-hour period from Sept. 22 to Sept. 24, 1980. He still faces charges in one of those deaths, and additional charges stemming from nonfatal knife attacks on black men in Buffalo on Dec. 31, 1980, and Jan. 1, 1981. In addition, he has been indicted in Manhattan on charges of killing a Hispanic man and attacking a black man with a knife on Dec. 22, 1980.