Objective To explore the effect of Heshouwuyin(HSWY) on the expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) protein in testis tissue of overtrained rats. Methods Thirty SD rats were randomized into 5 groups, including normal control group(A group), HSWY administered normal group(B group), model control group(C group), HSWY treated group (D group), HSWY beforehand-prevented group (E group), 6 animals in each group. The model of C, D and E group were made by overtraining, the D group was treated with HSWY by intragastric administration for 60 days after the success of model［20g/(kgI>&#/I>8226;d) including crude drug 9.6kg/L］, and the E group was prevented by administering HSWY before overtraining［20g/(kgI>&#/I>8226;d) including crude drug 96kg/L］. The density of testosterone was detected by radio-immunity, the expression of 3β-HSD was measured by immunohistochemistry, Western blotting and RT-PCR. Results Compared with C group, 3β-HSD protein was expressed in plasmid of leydig cells, and the expressions of 3β-HSD and 3β-HSD mRNA in D group and E group were increased(EM>P/EM>0.05) with no differenc