Abstract： Objective To investigate the relationship between clue cell in semen and male infertility. Method Semen specimens from 957 patients were examined with microscope. Gram staining was performed when clue cell were found to be present in semen. At the same time, general characteristics of the sperm were analyzed. Results There were clue cells in 23. 5% (225/957) of the total specimens, in which, 95. 1% clue cells were gram staining positive. The concentration and vitality of living sperm in semen presented with clue cell were significantly lower, but the abnormal sperm and pH value were much higher than that in normal control (P<0.01). In addition, 28 sexual partners of 30 infertility patients were identified as having bacterial vaginosis. Conclusion Gardnerella vaginalis and short coccohacillus were mostly transmitted from infected sexual partner. It could cause squamous epithelial cell forming clue cell, and lead to infertility by chan-ging pH which mainly affect reproduction of the sperm. This study suggested that clue cell has a unique vale for the diagnosis of infertility causing by Gardnerella vaginalis and short coccohacillus.