Abstract: Objective To study different concentrateions of B (a) Pon enzyme activitiy,spermabnormality rate,and DNA damage rate of mouse germ cells.Methods Lactate dehydrogenase (LDH),glucose-6-phosphate dehydrogenase (G-6-PD),sorbitol dehydrogenase (SDH) were measured with spectrophotometry; DNA damage was detected with single cellgel electrophoresis(SCGE),and sperm abnormality rate and sperm cells micronucleus rate were determined with sperm aberration test and micronucleus test,respectively.Results B (a) P affected activities of LDH,SDH,G-6-PD in mouse testicular cells.The activities of LDH in testicular cells decreased with the increasing of B (a) P exposure dose,and significant defference was observed between 20 mg/kg group and the negative control group(P < 0.05).DNA damage was observed in every exposure group,with the damage rate of 44%,79%,and 88%,respectively,and all of the rate were significantly different from that of negative control group(P < 0.05).Sperm abnormality rate and sperm cellmicronucleus rate in each exposure group were 1.10%,2.24%,3.64%,and 11.00%,14.40%,17.40%,respectively,and were significantly different from that of the control group(P < 0.05).Conclusion B (a) P could influence enzyme activities of mouse sperm cell,cause DNA damage and have cytotoxicity to male mouse sperm cell within a certain dose range.