NEW YORK (AP) _ The three-year marriage of chicken magnate Frank Perdue and Kathleen Markey Perdue ended in divorce last week in Salisbury, Md., a spokesman for Mrs. Perdue's lawyer said today.

The terms of the divorce were not divulged, but Mrs. Perdue's lawyer, Marvin Mitchelson, characterized the split as ''very amicable,'' said the spokesman, Sy Presten.

The marriage of May 4, 1985, had been the first for Mrs. Perdue, 38, a former vice president of Salomon Brothers, the Wall Street firm.

Perdue, 67, whose chicken business is headquartered in Salisbury, had been married once before.