Objective To observe changes on membrane integrity and ultrastructure of human sperm after freeze-drying.Methods Semen samples from both normospermic donors(group A, n=15) and infertile men with abnormal sperm parameters(group B, n=15) were enrolled into this study. These samples were freeze-dried by using a freeze-drying method. The membrane integrity in the head and tail regions of individual spermatozoon was examined by using the combined hypo-osmotic swelling-eosin Y exclusion test. Sperm ultrastructure in groups A(n=3) and B(n=3) was observed by scanning electron microscopy(SEM).Results After freeze-drying, all spermatozoa were types I(damaged both head and tail membranes) and III(damaged head membrane and intact tail membrane) membrane integrity in groups A and B. Type III of group B had lower value than that of group A(P<0.01). Under SEM, intact freeze-dried spermatozoa including abnormal morphology and normal-looking morphology were observed in both groups A and B. A few freezedried sperm heads had unsmooth or fuzzy surface. Isolated sperm heads, bent tails,broken sperm tails or fragmentary tails were more frequently seen in group B than those in group A.Conclusion Freeze-dried human spermatozoa could have intact structural components. However, freeze-drying resulted in severe damage on membrane integrity and ultrastructure of sperm. Samples from infertile men would have less resistance to freeze-drying. Objective To observe changes on membrane integrity and ultrastructure of human sperm after freeze-drying. Methods Semen samples from both normospermic donors (group A, n = 15) and infertile men with abnormal sperm parameters (group B, n = 15) were enrolled into The study was done by using a freeze-drying method. The membrane integrity in the head and tail regions of individual spermatozoon was examined by using the combined hypo-osmotic swelling-eosin Y exclusion test. Sperm ultrastructure in groups A (n = 3) and B (n = 3) was observed by scanning electron microscopy (SEM). Results After freeze-drying, all spermatozoa were types I (damaged both head and tail membranes) and III (damaged head membrane and intact tail membrane) integrity in groups A and B. Type III of group B had lower value than that of group A (P <0.01). Under SEM, intact freeze-dried spermatozoa including abnormal morphology and normal-looking morphology were observed in both groups A and B. A few freeze dried sperm heads had unsmooth or fuzzy surface. Isolated sperm heads, bent tails, broken sperm tails or fragmentary tails were more frequently seen in group B than those in group A. Conclusions Freeze-dried human spermatozoa could have intact structural components. However, freeze -drying resulted in severe damage on membrane integrity and ultrastructure of sperm. Samples from infertile men would have less resistance to freeze-drying.