Abstract: The fecundity of fish and oocyte diameter are two important indicators of the reproductive potential of population. However, little is known about the temporal changes of fecundity and oocyte diameter during the spawning season. A total of 180 Hemiculter leucisculus individuals were collected monthly from April to October in the lower reaches of the Yuanshui River, 81 of which were matured female and their fecundity and oocyte diameter were analyzed. The results showed that the Gonadosomatic index (GSI) was the highest in May and June, intermediate in July, August and September, and the lowest in April and October. The average absolute fecundity (AF) was (30116±19390) oocytes, with a peak at 10000—30000 oocytes. The average relative fecundity (RF) was (650±324) eggs/g, with a peak at 400—800 eggs/g. The relationships of AF to standard length (SL) and AF to clear weight (CW) were as follows: AF = 0.009SL^3.009 (r²=0.56) and AF = 1392 CW^0.833 (r²=0.52) respectively. AF and RF were the highest in May and June, intermediate in July, August and September, and the lowest in April and October. The diameter of mature egg was not significantly different among months. The diameter of recruited egg was the largest in May and June, indicating the highest reproductive frequency. The result documented that batch fecundity and reproductive frequency changed with spawning periods, from which larvae make different contributions to population recruitment. Also, the temporal variations of batch fecundity offer important guidance in assessing reproductive potential of population. Fecundity of H. leucisculus showed spatial variations among habitats, and was higher for populations at lakes and reservoirs than in rivers. The fecundity in the Yuanshui River was similar to lakes and reservoirs, and it is a slow-flowing and lenticular habitats. The study revealed reproductive characteristics of H. leucisculus, which provides essential data bases for fishery management of this species.