Objective To study the effect of mitochondrial reactive oxygen species(ROS)on male fertility and its application value in assisted reproduction so as to provide a new method for fertility assessment and etiological treatment of male infertility.Methods The relationship between sperm ROS and male infertility,sperm nuclear DNA integrity and sperm membrane function was analyzed.Then the relationships of the ROS of sperms for fertiliza-tion with fertilization rate,cleavage rate,embryo rate and pregnancy outcome were analyzed.Results(1)The percentage of the high ROS in sperm membrane of the male infertility group was significantly higher than that of the normal fertility group(P<0.01),but there was no statistical difference in the percentage of the high ROS in the sperm mitochondria between the two groups.(2)The normal rate of sperm membrane function in the normal group was significantly higher than that in the abnormal group(P<0.01),but there was no significant difference in the sperm DNA fragmentation index(DFI)between the groups.(3)There was significant difference in the fertilization rate between the IVF control group and IVF observation group,but no significant difference was seen in the cleavage rate,excellent embryo rate and clinical pregnancy rate between the groups.Conclusion Sperm ROS is related to male fertility to some extent.Abnormal ROS may lead to impaired sperm membrane function and affect sperm fertilization ability,thus affecting male fertility.The detection of ROS in sperm can be used as a new method to evaluate male fertility and provide a basis for diagnosis or treatment of male infertility.For patients with ART or infertility,the appropriate time to conceive can be selected according to the sperm ROS level.