Objective:To identify and analyze the differential expression of L-lactate dehydrogenase B chain(LDH-B)in the penis of rat offspring after maternal exposure to di-n-butyl phthalate(DBP). Methods:Twenty pregnant rats were randomly divided into two groups and given DBP by gastric intubation at the dose of 800 mg/kg per day in the experimental group or 5 ml per day soybean oil in the control group from the 14 th to 18 th day of pregnancy. Penises were harvested from the fetal rats of the normal and exposed groups respectively at GD l9 .The expression of LDH-B detected and analyzed by Western blot and immunohistochemistry. Results:LDH-B expressed both in the experiment group and the control group,but the expression level is much lower in the experimental group than in the control group(P < 0.05). LDH-B was mainly located in the cytoplasm of the penis’s tissue. Conclusion:LDH-B protein expressed much lower in the penis of the rat offspring after maternal exposure to DBP than in the penis of the rat offspring without exposure to DBP.