Objective To investigate the mechanism of DEHP and DES on cryptorchidism in prepubertal SD rats. Methods Forty-eight pregnant SD rats were randomly divided into six groups:1) control group; 2) corn oil group (1ml / d); 3) DEHP low dose group (100 mg/kd/d +1 ml corn oil /d); 4) DEHP medium dose group (500 mg/kg/d+1 ml corn oil /d); 5) DEHP high doses group (750 mg/kg/d+1 ml corn oil /d); and 6) DES (100 mg/kg/d+1 ml corn oil /d). From GND12 day to PND3, each group of rats was administrated each of the above treatment. Thirty days after F1 pups were born, the incidence of cryptorchidism in male offspring rats in each group was calculated. The pathological section of testis was prepared in each group. The amount of testosterone in rat offspring was measured with chemiluminescence method. The relative expression of the cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc) mRNA, acute regulatory protein (Star) mRNA enzymes and 3β steroid dehydrogenase (3β-HSD) was measured with real time PCR. Results 1) Exposure to DEHP and DES at embryonic period caused prepubertal SD rat cryptorchidism; 2) Leydig cells suffered varying degrees of damage in the medium and high dose of DEHP group and in the DES group; 3) Compared with the normal group, levels of testosterone (T) in the medium and high dose DEHP group and in the DES group were significantly reduced (all P<0.05); 4) DEHP and DES had an impact on gene expression of key enzymes in the synthesis of testosterone formation. The expression levels of P450scc and 3β-HSD mRNA were reduced; the expression of Star enzymes mRNA was increased in low, medium and high dose of DEHP groups. The expression levels of P450scc, 3β- HSD, and Star enzymes mRNA were reduced in the DES group. Conclusion Exposure to DEHP and DES can directly affect Leydig cell, resulting in decreased testosterone. On the other hand, the exposure can affect the process of transcription of testosterone production, resulting a reduction of testosterone. However, the results of DES and DEHP on androgen related enzymes in rat were slightly different, suggesting that the mechanism warrants further study.