Objective To explore reproductive toxicity of Trichlorfon in male mice. Methods Forty male ICR mice were randomly divided into three exposure groups (2, 10 and 50 mg/kg dose of Trichlorfon) and control group (equal volume of saline), and each group included 10 mice. All mice were exposed orally once per day for 30 d continuously, then the mice were sacrificed by cervical dislocation. The rates of sperm motility and sperm shape abnormality were measured, and histopathological changes of testis were observed. The relationship between dose of Trichlorfon and sperm motility and abnormality was analyzed. Results Compared to control group, the percentage of sperm motility in exposure groups changed remarkably, where the percentage of Ⅲ and Ⅳ grades increased in all exposure groups and Ⅰ and Ⅱ grades decreased in 50 mg/kg group (P<0.05, P<0.01). The percentage of sperm abnormality increased significantly (P<0.05) (control group: 0.38%, 2 mg/kg group: 1.00%, 10 mg/kg group: 2.06%, and 50 mg/kg group: 3.39%). The changes for sperm motility and abnormality were presented in a dose-dependent manner. Pathologic observation revealed that the number of spermatocytes in somniferous tubules was reduced in the 10 mg/kg and 50 mg/kg groups. Conclusion Exposure to Trichlorfon may cause reproductive toxicity in male mice.