To investigate the effect of administration of MPA with/without TU on serum sexual hormones and spermatogenesis of male rats.Twenty rats had been classified into four groups. Each group received injection of saline(group A) or MPA(37.5 or 75 mg/kg) (group B or group C, respectively) or MPA (75 mg/kg) + TU (25 mg/kg) (group D) every month during three months. Data from serum sexual hormones (FSH, LH, T), sperm counting and motility had been collected and analysed.Spermatogenesis of rats undergoing administration of MPA with or without TU had been suppressed. Serum FSH and LH of group B, C, D declined, and so did serum T of group D. Testis of rats of group D atrophied and sperm counting of group D decreased remarkably compared with group B and C. But there was no statistics difference of the sexual hormone level among group B, C and D.Administration of MPA alone could suppress the levels of FSH and LH and block the spermatogenesis of male rats. MPA combined with TU could offer stronger suppression on spermatogenesis. Mechanism of the suppression on spermatogenesis of MPA + TU is not only limited in the feed-back of gonadotropin, but there maybe exist a direct suppression on testis.