Neutral alpha-1,4-glucosidase (NAG) is a crucial biomarker for the function of epididymis and is reported to be associated with semen quality. However, the correlation between NAG and Chinese semen quality has never been reported. This study aimed to investigate the level of NAG in the seminal plasma of Chinese men. A total of 394 cases of seminal plasma samples from normal, subfertile and infertile men were enrolled in this study. Male subfertility was caused by teratozoospermia, asthenospermia, severe oligozoospermia, asthenoteratozoospermia, oligoasthenospermia and oligoasthenoteratozoospermia. Male infertility was resulted from azoospermatism. The level of NAG was detected by spectrophotometry. Results showed that the level of NAG in normal men was significantly higher than that in subfertile and infertile men (p = .000). Meanwhile, the level of NAG in subfertile men was significantly greater than that in infertile men (p = .000). In addition, a significant difference was observed in normozoospermia, teratozoospermia, asthenospermia, severe oligozoospermia, asthenoteratozoospermia, oligoasthenospermia, oligoasthenoteratozoospermia and azoospermatism (p< .05). In conclusion, these data indicate that NAG is a crucial marker for assessing seminal plasma quality in Chinese men, which might be helpful for the assistant diagnosis of male infertility.