Based on the data from four seasonal oceanographic censuses in the East China Sea （23?30′ - 33?N, 118?30′ - 128?E） in 1997 - 2000, this paper discussed the ecological characters of the dominant species of Decapods in the East China Sea and significance in the form of fishing ground. Results showed that there were four dominant species of Decapods, Lucifer intermedius, Leptochela gracilis, lucifer penicillifer and leacifer hanseni, leacifer intermedius and leacifer penicillifer were warm-water species offshore, lucifer peniclllifer was warm-water sea species. Leptochela gracilis was eurythermic halobiotic species. The warm-water species offshore exhibited not only higher abundances but also bigger average dominance and abundance percentages of dominant species in total abundance than other species. The eurythermic halobiotic species usually exhibited higher occurrence frequency. For example, Leptocheia gracilis occurred in every district and season in the East China Sea though its abundance was relatively lower. Analysis in aggregation intensity of dominant species showed that the warm species with poor ability of adaptation to low temperature showed higher aggregation in summer. That was why the aggregation intensity of Lucifer peniciUifer and Lucifer hanseni was higher than that of Lucifer intermedius in that season. Different from other zooplankton in the East China Sea, the dominant species of Decapods showed such ecological characters as highest abundant level in summer, individuals of stenohaline species in most, distribution in costal and estuary near the fish spawn ground, which were very important in the fishery.