Abstract: Comparative study was conducted on the species composition, dominant species, density, biomass, and biodiversity index of zooplankton along the Liaoning coast of the Bohai Sea and the Liaoning coast of the North Yellow Sea, as well as their relationship with environmental factors which was based on the marine survey data conducted by the National Marine Environment Monitoring Center in the Yellow and Bohai Seas from 2018 to 2022. Over the past five years, a total of 75 species of zooplankton were identified in 9 classes along the coast of the Bohai Sea and the North Yellow Sea, belonging to 43 families and 52 genera, as well as 23 classes of zooplankton larva; A total of 39 species of zooplankton have been identified in both sea areas, as well as 18 classes of zooplankton larva. There were 17 species of zooplankton identified only along the Bohai coast, with 2 unique types of zooplankton larva; Only 19 species of zooplankton was appeared along the North Yellow Sea coast, with 3 unique types of zooplankton larva. Paracalanus parvus and Sagitta crassa are perennial dominant species in both sea areas. The zooplankton species in the two areas were relatively similar but the dominant species were certain difference. There are significant differences in zooplankton density, biomass and biodiversity index mostly between the Bohai Sea coast and the North Yellow Sea coast. The average densities of the shallow water Type I plankton net (hereinafter referred to as Type I net) zooplankton along the Bohai coast was a little more than along the North Yellow Sea coast in the mass, the average density of the shallow water Type II plankton (hereinafter referred to as Type II net) zooplankton along the Bohai coast was slightly lower than along the North Yellow Sea coast in the mass. The average biomass of zooplankton along the Bohai coast was a little more than along the North Yellow Sea coast in the mass, the most obvious in autumn. The average diversity index values of Type I net zooplankton along the Bohai coast were slightly decrease in autumn, and the average values of richness index of Type I net zooplankton along the North Yellow Sea coast have increased. Temperature, salinity and suspended solid were the very significant differences (P＜0.001) between the Bohai Sea coast and the North Yellow Sea coast. Temperature, salinity and dissolved oxygen were the main environmental factors that affected the zooplankton community structure in the two sea areas. The results of this study can provide reference for the protection of ecological system of the Bohai Sea and North Yellow Sea along the coast of Liaoning.