Abstract: Cyclops vicinus vicinus Uljanin is the dominant copepoda in the Lake Donghu, Wuban. The development times of the eggs, nauplii and copepodites of C. vicinus vicinus were obtained by experiments at constant temperatures ranging from 6.5 to 25℃.The duration of egg development was obviously inversely related to temperature through the whole range of experimental temperatures. Development times of nauplii and copepodites were decreased with increasing temperatures and retarded at temperature above 20℃. The relationships were expressed by various regression equations.The female body was generally longer than that of the male, and smaller adults were generally produced at higher temperatures. The longevity of the adult stage was inversely related to temperatures.The duration from the hatching of one brood to the extrusion into eggsacs of the next brood and the average time from the adult to the production ot the first eggsacs were also decreased as temperature increased. The present results also showed the inverse relationships between clutch size, clutches per female and temperatures. The effect of diet on development of C. vicinus vicinus was also discussed in this paper.