Abstract: To study the spatial and temporal distribution of fish stock density and diversity in the outlet of Hangzhou Bay during different seasons, sweep area method, Shannon-wiener diversity index (H') and Spearman correlation analysis were applied to variety analysis of fish species and density. The results showed that 22 species including 12 species in spring and 20 species in summer were found in the outlet of Hangzhou Bay. There were significant differences of fish species between spring and summer (Q=5.333, P=0.021<0.05). Weight density and individual density of fishes were 17.80 kg/km² and 2.32×10³ ind./km² in spring, respectively, and were 234.35 kg/km² and 21.64×10³ ind./km² in summer, respectively. There were significant differences of fish density between spring and summer. The average weight H' and individual H' were 0.98±0.43 and 1.28±0.50 in spring, respectively, and were 1.17±0.45 and 1.16±0.38 in summer, respectively. Spearman correlation analysis indicated that individual H' was closely related to fish species (P=0.000<0.05, R=0.912) and individual density (P=0.011<0.05, R=0.758) in spring, while only fish species was closely related to weight H' (P=0.033<0.05, R=0.673) and individual H' (P=0.009<0.05, R=0.772) in summer. The research indicated that the spatial and temporal distribution of fish stock density was related to the migratory habit of marine fishes in the outlet of Hangzhou Bay during spring and summer, and the spatial distribution of fish stock diversity was probably influenced by the diluted water of the Yangtze River.