A total of 1983 fish individuals, representing 23 species from 18 genuses 9 families, were collected auratus and Ctenogobius giurinus, accounting for 40. 09%, 20. 52% and 10. 29% of total samples respectively. Hypophthalmichthys molitrix, Carassius auratus, Cyprinus carpio, Aristichthys nobilis were the main economic species, whose fry come from aquaculture. Diversities of fish were represented by species abundance, average abundance, diversity index, evenness index, dominant index and relative rare species. Current diversity index was 1. 899 6, 49 % lower than that in 1959. Evenness index showed a decreasing tendency. The dominant index had increased from 0. 034 in 1959 to 0. 226 4. The fish species diversity has been declining, which may be attributed to the deterioration of habitat environment and effect of human activity such as overfishing.