To investigate the characteristic of antibodies that induce the rejection of xenografting,SD rats were immunized with NIH mice spleen to prepare rat antimouse antiseras. The antibodies were purified by caprylic acid precipitation and hydroxy lapatite(HPT)chromatography.The results showed that the title of rat antimouse antisera was 1∶640,and the antibodies purified by caprylic acidHPT had reliable purity and good immunocompetence.This method coule be used in preparation and research of major histocompatibility antibodies.