Sperm quality evaluation is an important part in male reproductive biology.In spite of numerous studies on mammalian and fish,there are few related reports on crustacean,even no reports on Chinese Mitten Crab(Eriocheir sinensis).Eosin staining and trypan blue staining are two common methods for detecting cellular viability rate and both are used for evaluation of sperm quality.In this paper,sperm viability rate of E.sinensis was investigated with eosin staining and trypan blue staining.The results showed that there were significant differences of staining characters between dead and live spermatozoas:the live ones were transparent,while the dead ones were stained easily by either dye.We found that 0.25% eosin solution and 0.5% trypan blue solution stained the most effectively,and the optimum reaction time was 15 min.We also showed that there was positive correlation between pratical and theoritical values when either of the two dyes was used(P0.05) and there was also positive correlation between these two staining methods(P0.05).These results suggested that both eosin staining and trypan blue staining were suitable for evaluation of sperm viability rate of Chinese Mitten Crab.