The effect of loss-of-function of Attractin (Atrn) on the male mouse reproduction system was examined in the study. The weights and pathological changes of testes and epididymes were compared between Atrn mutant (Atrn(mg-3J)) mice and wild-type mice (C3HeB/FeJ) at different months of age. The number and motility of sperms were measured in the mutant and control mice. Furthermore, the testicular lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) in these animals were detected. The fertility potential of the sperms was observed in vivo and in vitro. The results showed that the testes of 3-month-old Atrn (mg-3J) mice experienced no significantly different pathological changes from the control mice at the same month of age but the SDH activity was substantially reduced. In the 5-month-old mutant mice, as compared with the control mice, mild vacuolation was found in the testes, the density and motility of sperms were decreased in the epididymes, the sperm fertility was impaired and the testicular enzyme activity was reduced. It is concluded that the age-related Atrn gene progressively loses its function and can cause testis vacuolation and impaired sperm function, which may be responsible for the impairment of male reproductive ability.