Abstract: The results show that the sexual gland of Chinese suoker blocked by the dam can develop aad maturate normally in. the downstream. Sexual maturity is reached at age 7⁺ for females, over 5⁺ for males.The ovaries of stage II (inclu-ding stage II after spawning)，IV, V, VI and the testes of stage II,III(including stage III after spawning)，IV, V, VI were collected. Meanwhile, the microscopical structure charactaristios of ovaries and testes were observed. Altogether 138 specimens were collected in 1983--1990. 55 of them are matu-rity, constituting 39 .86%of the total and 83 of them are immature, constituting 60.14%.The mature females are 82----110cm in TL, 94.50± 7 .21cm on average; 9 .2-20kg in weight, 14.39 ± 3 .46kg on average. While the males 76.5--108cm in TL,92 . 67± 7.69cm on average; 8--18 .25kg in weight, 12.28 ± 2.48kg on average.The females collected at the age of 7-14 and males 5-14. Sexual ratio of female to male is 1:1.39.Absolute fecundity is from 215,000 to 422，500 eggs, average fecundity is on the order of 286, 800 eggs per females;relative fecundity 13.48-21.66 egg/g, average 16.89egg/g.In late autunnn and early winter, the adults move from the middle and lower reaches of the river to the section below the dam，and often stay in deeper water.By spring, from the end of h'ebruary to the and of April, the parents move into some areas where current is swift and gravel covers the bottom far spawning.Spawning is chiefly related to temperature and most occurs in the fine morning.The problems of protective for Chinese sucker in the Iower reaches of the dam are discussed as well.