Abstract: To investigate the issue specifical characterics of human cardiac myosin light chain-1 （CMLC-1）,the changes in CMLC-1 isoforms expression during the development and the evolutionary relationships of the CMLC-1 isoforms in different species of mammalian animals, we examined CMLC-1 in adult and fetal human hearts and other tisssues and mammalian hearts immuohistochemically by using of the monoclonal antibody against human ventricular light chain-1 （MabVLC-1）. The results showed the adult human ventricle and slow-type skeletal muscles were strongly crossreacted with MabVLC-1, and the human adult atria and fetel ventricle were moderately crossreacted with MabVLC-1;and other human tissues including fast type skeletal muscle, smooth muscle and liver or spleen were not crossreacted. The degree of the fetal ventricle crossreacted with MabVLC-1 increaced with advance of the fetal ages. The heart tissues of all kinds of mammalains were crossreacted with MabVLC-1,and the reactivity increaced with the evolutionary degree of the mammlain species. The results suggest that （1） The CMLC-1 express specially in the ventricl and slow-type muscles;（2）The expression of the CMLC-1 in ventricle is developmentally and evolutionaryly getting move.