To analyze the activity of human sperm acrosin and semen parameters in male infertile patients and discuss the effect of sperm acrosin activity on semen quality. Activity of human sperm acrosin, PMN-elastase, fructose, alpha-glucosidase, zinc, acid phosphatase levels and HOST of 214 male infertile patients were detected. Semen analysis was performed using WLJY-9000 WeiLi colorful semen quality analyzer. There were 111 cases of normal activity of human sperm acrosin (48.2 - 218.7 microIU/10(6) sperm), 103 cases abnormal (< 48.2 microIU/10(6) sperm). Using the group of normal activity of sperm acrosin to be the control, semen parameters was analyzed and compared with those of the group of abnormal activity of sperm acrosin. There were significant difference (P < 0.001) between the 2 groups (normal and abnormal) in the areas of sperm density, motile sperm rate, percentage of grade (a + b) sperm and HOST. There were also significant difference in PMN-elastase, fructose and alpha-glucosidase (P < 0.05). There was no difference among sperm volume, zinc and acid phosphatase (P > 0.05). There was a strong correlation between the activity of human sperm sperm acrosin and semen quality. Activity of sperm acrosin is a reliable index of semen quality.