Abstract: Objective To evaluate the effects of mustard gas on reproductive toxicity to male rats.Methods 40 SD male rats were injected with mustard gas.After they recovered they mated with normal female rats and their male babies also with normal female rats.Then their epididym were obtained to detect number,survival rate of sperm.To write down the time of mating,number,mortality and gender of baby rats.Results The time of mating in male rats were magnificantly longer than control group,number of sperm was less.Surviving rate was lower and malformation rate was higher.The number and survival rate were significant lower than control group in the first filial generation and the number of sperm was not significantly different.Surviving rate was lower and malformation rate was higher.The number of the second filial generaton was not significantly different compared with control group,but mortility were significantly higher.Gender was not significantly different.Conclusion Damage of mustard gas on male rats'reproductive system was serious and long-time effect can go down to the future generation.