In order to assess the relative trophic importance of the spotted velvetfish in Changjiang Estuary and adjacent sea in summer, carbon(δ¹³C) and nitrogen(δ¹⁵N) stable isotope ratios were determined in spotted velvetfish and its potential food sources. Based on an organism's stable isotope ratios are an integration of the isotopic signatures of food sources that have been assimilated through time. The δ¹³C and δ¹⁵N values showed that the spotted velvetfish's food sources were composed of plankton >900 μm, Leptochela gracilis, common squid, Lantern cuttlefish, Beka squid, Common Japanese squid, larvae and juvenile and Japanese sand shrimp. plankton >900 μm was the most important food source, accounting for 69%-75% of the total food by weight. Food proportion of the spotted velvetfish varied among different classes of sizes. Cluster analysis dived the body lengths of the spotted velvetfish into two groups according to stable isotope ratios, >60 mm and <60 mm, respectively. The food proportion of the plankton >900 μm was 68%-87% to 75%-88% for the > 60 mm to <60 mm, while the proportions of larvae and juvenile，mollusk，Crusta ceans to the larger group have a degree of increasing. The proportions of all food sources showed that plankton >900 μｍ was the most important prey, while others were eaten occasionally by the spotted velvetfish. If the production of plankton >900 μｍ decrease in some cases, the spotted velvetfish would increase the other food proportion, sharing the large size food with other org anisms,which would decrease the production of high trophic level organisms or s horten the length of food chain.