Abstract: The volume of matUre teshs of black flnless porpoise in the Yangtze Riverwas large.Its weight was almost 14 hmes that of prematUre individual.Consideringsome records of captUre and ecological inveshgahon of black finless porpoise, itSreproduction population reproduchon was Perhaps polygyny in the Yangtze River.Soit is estimated that large testis of mature male was favorable to succesive reproductionof populahon.The histological development process of teshs was divided into earlystage of embryo, late stage of embryo, prematUre stage and matUre stage (achve andinachve testis) in the paPer.Seasonal changes of matUre teshs of black finlessPorpoise was proved by the study of seminiferous tubule and tunica albuginea.