Distribution patterns and abundance of the euphausiids were examined in the East China Sea (23°30 ′-33°00′N、118°30′-128°00′E), in relation to temperature and salinity. The data were collected in 4 surveys from 1997 to 2000. The Density or Yield Density model was used to predict optimum temperature and salinity of water for euphausiids occupations, thereafter, distribution patterns of euphausiids were determined based on the predicted parameters. Of 23 species, Euphausia pacifica, E. nana, Pseudeuphausia sinica, and P. latifrons were numerically dominant. The analyses indicate that Euphausia pacifica is an offshore temperate water species, E. nana is an offshore temperate warm water species, P. sinica is a coastal subtropical water species, and P. latifrons is an oceanic tropical water species. The four species occupied four different water masses, respectively, cold water mass, transitional zone where cold and warm water masses are mixed in the winter and spring, transitional zone where cold and warm water masses are mixed in the summer and fall, as well as warm water. These could be the designator of individual water masses, respectively. The predicated optimal temperatures for E. tenera, S. carinatum，E. diomedeae，Stylocheiron affine, Nematoscelis sp., N. gracilis, N. atlantica, Stylocheiron sp. and S. suhmii are all > 25℃. These species are mainly distributed in southern Kuroshio in the winter and spring, the Kuroshio, the Taiwan Warm Current and Tsushima Warm Current during the summer and autumn, and the equatorial waters of Pacific Ocean and the eastern waters of Taiwan. They are designated as oceanic tropical water species. Nematoscelis tenella and T. tricuspidata are referred to as offshore subtropical water species according to their geographic distributions, even if they are halobionts. Euphausia sanzoi is considered as a typical offshore subtropical water species, which inhabited waters below 25℃. Stylocheiron microphthalma, occupied warm current waters where temperature and salinity is nearly 25℃, 34 ppt in the summer and autumn, is designated as oceanic tropical water species. In the same way, E. similes, E. mutica, Euphausia sp., E. brevis and E. recurva are classified into offshore subtropical water species in accordance with the optimum temperature and salinity of waters, as well as locations and seasons of their occurrence. Optimum temperature, rather than salinity is a better parameter in determining the distribution patterns of euphausiids.