Effect of environmental factors on the activation of spermatozoa of Chinese ocellated sleeper, Bostrichthys sinensis ( Lac.p .de) , was studied. The optimum activat ing salinity for the spermatozoa was 5- 15. The activation of the spermatozoa concerned with not only osmosis or salinity, but also with composition of solution. The function of K+ was represented as a restraining factor to activation and movement of the spermatozoa in the present condition. The spermatozoa had a strong adaptability to the variation of pH, and the activating rates were more than 70% while pH of the activating solution varied from 5. 5 to 9. 5. The optimum pH of the activating solution was neutral or weak acidity for the spermatozoa, the swimming time of the spermatozoa was the longest when pH was 6. 0. The spermatozoa of Chinese ocellated sleeper were cryopreserved successfully by using a simple procedure . Sea water with salinity 40 or a solution containing 1. 5% NaCl , 1 . 5% KCl , 0. 25% CaCl2 and 0. 25% MgCl2, was practical extender for cryopreservation of Chinese ocellated sleeper spermatozoa. DMSO was an effective cryoprotectant, and its optimum concentration was 10% in this study. The activation rates of the pos-t thaw spermatozoa were almost as good as the control. s , namely fresh spermatozoa, and their fertilizat ion rates were over 80%, approaching the control. s.