Objective:To verify the differential expression of Lamin B1 in the penis of rat offspring after maternal exposure to di-n-butyl phthalate(DBP)in order to explore the mechanism of hypospadias. Methods:Twenty pregnant SD rats were randomly divided into two groups acting as experiment group and control group,which were respectively given DBP and soybean oil gavage at the dose of 800 mg/(kg·d)and 2 ml/d since the 14~18 th day of pregnancy,anogenital distance(AGD),birth weight(BW),hypospadias incidence were recorded,and penises of fetal rats were harvested at GD19. The expression of Lamin B1 was analyzed by Western blot and immunohistochemistry. Results:The incidence of hypospadias was 40%,and the AGD/BW of experiment group was significantly lower than control group(P < 0.05),and the expression of Lamin B1 had statistical difference between two groups(P < 0.05). Lamin B1 was mainly located in urethral epithelium in the developmental phase of the penis,and the control group staining intensity was stronger than the experimental group. Conclusion:Maternal exposure to DBP can reduce the Lamin B1 expression in urethral epithelium,affect cellular migration and urethral fold fusion,and then result in the occurrence of hypospadias.