Abstract: An investigation on the species composition and biodiversity of fish community in Chongming Dongtan of Yangtze River estuary was made in MayAugust,
2004-2006. A total of 39  species were collected, belonging to 37 genera, 22 families, and 14 orders. The dominant species were Saurogobio dumerili, Lateolabrax maculatus, Cynoglossus gracilis, Coilia ectenes, Liza haematocheila, and Mugil cephalus. Perciformes was most abundant, followed by Cypriniformes. The fish community could be classified into 4 ecological types, i.e., freshwater fish (13 species), estuarine fish (4 species), migratory fish (6 species), and marine fish (16 species). The eigenvalues of species diversity were Margalef’s index (R) being 2.30, ShannonWiener’s index (H′) being 1.95, Wilhm’s index (H″) being 2.17, McNaughton’s indices D_n and D_w being 0.60 and 0.45, respectively, Simpson’s index (C) being
 0.22, and Pielou’s index (J′) being 0.59. In the fish community, small with a mean body weight less than 50 g were the most superior in numbers, the
 capture size of commercial fishes became smaller, and the biodiversity decreased. It’s needed to strengthen the conservation and restoration of key fish species and their important habitats to protect the fish resources in Chongming Dongtan.

Key words: Automobile exhaust, Leaf cell pH value, Relative conductivity, Chlorophyll, Malondialdehyde, Superoxide dismutase, Peroxidase, Ascorbic acid