Objective To investigate the factors affecting cryopreservation of mouse sperm.Methods Mice sperm from C57BL/6J,FVB/NJ,B6D2F1 and ICR strains were cryopreserved using 18% raffinose,3% skim milk as cryoprotectant solution,and estimated the survival and fertility of post-thawed sperm from the five strains.The progressive motility of sperms from each strain was affected differently.Results The fertility rate of C57BL/6J,FVB/NJ,B6D2F1,KM and ICR strains were significantly decreased from 81.4%,87.2%,90.4%,82.7% and 79.4%,respectively,of fresh sperm,to 6.7%, 46.0%,76.8%,59.2% and 31.9%,respectively,when using post-thawed sperms(P<0.01).Conclusion The fertility and susceptibility to cryopreservation of sperm from mice of different genetic background differ significantly.