To study the effect of DEHP on testis development and the related gene expression in prepubertal male rats after 28 days exposure in order to explore the mechanism of genital toxicity.The prepubertal Wistar rats were lavaged consecutively for 28 days with the DEHP dose of 10,100 and 1000 mg x kg(-1) x d(-1). The change of body weight and status were observed dynamically. After decapitation 28 days later,the organ coefficient of testis was measured. Meanwhile the morphological changes of testis and epididymis were observed by HE staining under optical microscopes. The total RNA of testis was extracted and cDNA synthesis was followed as the manual instruction of RT-PCR kit. The effect of DEHP on gene expression of StAR, CYP19a1 and CYP11a1 was compared to each other in different DEHP group.The body weight growth of rats in 1000 mg/kg DEHP group was restricted compared with the control (F = 3. 54, P < 0.05). Both the weight and the organ coefficient of testis were also degraded, and there were statistical significance between the 1000 mg/kg DEHP group and the control (F = 105.545, P < 0.05). The serious morphological changes of testis and epididymis were shown in 100, 1000 mg/kg DEHP group. In addition, the distinct difference in the gene expression of StAR wasn't shown in the study. On the other hand, CYP19a1 and CYP11a1 showed significant changes compared with the control due to the DEHP treatment.DEHP could influence the expression of aromatized enzyme such as CYP19a1 and CYP11a1, and then induce genital toxicity in male rats during the developmental phase.