To study the effects of ephedrine on histological structure of testis and on expression of Bax protein and epidermal growth factor (EGF)in the testis of the developing young mice (Mus musculus), ephedrine was administered by intraperitoneal injection at different doses. The testis structure was observed by microscopy and expression of Bax protein and EGF in the testis was measured by immunohistochemistry combined with stereological method at different developmental stages. Results indicated that the diameter and epithelium thickness of seminiferous tube significantly decreased in the experimental groups (P<0.01 or P<0.05). The diameter of primary spermatocyte was smaller than that of the control group (P<0.01 or P<0.05). Spermatogenic cells in seminiferous tube appeared late,and the cells loosely distributed,with more space between them, in the treatment group. At maturity there were less mature spermatozoa in the lumen of seminiferous tube. The expression of Bax protein and EGF in the testis of ephedrine-treated young mice significantly increased (P<0.01 or P<0.05). So the testis structure of young mice at different developmental stages were damaged to different degrees by ephedrine,which led to slow development of gonad. Therefore, ephedrine may affect spermatogenesis by altering status of primary spermatocytes and testis damage may be correlated with the expression intensity of Bax protein and EGF in young mouse testis.