Abstract: Using the methods of histology and histochemistry,the thymus and spleen of mice injected with cor-tison acetate were observed.This study showed that ANAE negative part of small lymphocytes in the cortex of thymus were the most sen-sitive to cortison acetate;the com-pensatory capacity of thymus of the adult mice was lower than that of the iufant mice;after phar-mocologic action disappeared,the number of T-lymphocytes in peri-pheral lymph organ was not easily reversed,the germinal centres app-eared later,so that the immunolo-gical function was definitely inf-luenced.This study also provided the normal data of ANAE positive lymphocytes in the thymus and TDA, of the spleen of the mice lived for 1,2,3,5,7,10,20,30,days respectively.