In order to explore the population structure of the aquatic organism and fish productivity in Xinghai lake, an investigation and analysis was carried out on the seasonal changes in density and biomass of the aquatic organisms in Xinghai Lake from April, 2016 to January, 2017. The results showed that there were 73 species of phytoplankton from 7 phyla and 58 genera in Xinghai lake, which has the largest amount of species in autumn and smallest amount of species in winter, the highest density in summer and the lowest density in winter, among which blue algae was dominant in summer and green algae was dominant in winter; There are 31 species of zooplankton, including 18 rotifers, 10 cladocerans and 3 copepods, which has the largest amount of species in spring and smallest amount of species in winter, the highest density in summer and the lowest density in winter,  the highest biomass in autumn and smallest amount of species in winter; There were 25 species of zoobenthos, belonging to 3 phyla, 4 classes and 16 families, among which there are up to 9 species of insecta species, which has the highest density in summer and the lowest density in winter, the highest biomass in autumn and smallest amount of species in winter; There were 33 species of aquatic vascular plants belonging to 23 families, which has the highest density in summer and the lowest density in winter, the highest biomass in summer and smallest amount of species in winter. The results showed that plankton and exogenous food in Xinghai Lake could support the productivity of silver carp and bighead carp for 194.48 kg/ hm2 each year, benthic and crustacean could support the productivity of omnivorous fish for 32.29 kg/ hm2, and aquatic plants support the productivity of fish for 291.5 kg/hm2. The reasonable stocking rate for silver carp is 149 kg/hm2, squid is 131 kg/hm2, omnivorous fish is 32.2 kg/hm2, and herbivorous fish is 0.8 kg/hm2 in Xinghai Lake.