A field fish survey of Dalian Lake, Shanghai was undertaken in Apr. 11-19, Apr. 27-May 8 and May 20-29, in total 24,061 fish individuals were collected, representing 22 species from 17 genera and 11 families. The dominant specie is Carassius auratus, accounting for 76.38% of the total. The eigenvalues of species diversity were showing below : Shannon-Wiener’s index (H¢) being 1.0027, Simpson’s index (l) being 0.5959, Pielous’s index (J¢) being 0.3244, Margalef’s index (D) being 2.0816 and relative rare species (R) being 90.91%. The fish community could be classified into 3 ecological types, which including river-sea migratory fish (3 species), river-lake migratory fish (1 species) and sedentary fish (18 species). Also they can be subcategoried into five types according to feeding habits, i.e., piscivorous fish (9 species), invertebrativorous fish (2 species), omnivores fish (7 species), planktotrophic fish (3 species), herbivorous fish (1 species). The results suggested that the biodiversity index and fish community stability are both at a low level. Compare to the lower reaches of Huangpu River, the proportion of piscivorous fish in Dalian Lake is higher, which suggested the water quality of Dalian Lake, located in the upper reaches of Huangpu River, is better than that in the downstream. It’s required to intensify supervision and strengthen the environment protection of Dalian Lake to guarantee the sustainable development.