Aim:To investigate the mechanism of infertility induced by varicocele and analyze blood gas in patients with varicocele.Methods:The left spermatic and peripheral vein blood were taken from 30 patients with varicocele and 25 normal cases,and the blood gas was measured.Results:pO2,oxygen saturation and O2Hb of the left spermatic vein blood were lower than those of the peripheral vein blood from the patients with varicocele(P0.05),but the pCO2,pH and other indexes between them had no significant differences(P0.05).All the indexes of blood gas had no significant difference between the spermatic and peripheral vein blood from the normal control(P0.05).Conclusion: The depression of pO2,oxygen saturation and O2Hb in the spermatic vein blood may explain why varicocele can result in infertility.