Abstract: Based on the marine survey data in the Yellow and Bohai Seas collected by the National Marine Environment Monitoring Center from 2018 to 2022, this study analyzed and compared the zooplankton species composition, dominant species, abundance, biomass, diversity and their relationships with environmental factors in the Liaoning coastal waters of the Bohai Sea (hereafter referred to as the Bohai coastal waters) and the Liaoning coastal waters of the North Yellow Sea (hereafter referred to as the North Yellow Sea coastal waters). Over the past five years, a total of 75 species of zooplankton belonging to 9 phyla, 43 families and 52 genera, along with 23 categories of zooplankton larva were identified in the two regions. A total of 39 zooplankton species and 18 pelagic larval categories were identified in both areas. There were 17 zooplankton species and 2 pelagic larval categories were found exclusively in the Bohai coastal waters; and 19 zooplankton species and 3 pelagic larval categories were found exclusively in the North Yellow Sea coastal waters. Paracalanus parvus and Sagitta crassa are perennial dominant species in both regions. The zooplankton species similarity between the two areas was relatively high, but there were certain differences in dominant species. Significant differences were observed in zooplankton abundance, biomass, and diversity indices between the two regions. The average zooplankton abundance based on Type I nets in the Bohai coastal waters was generally slightly higher than that in the North Yellow Sea coastal waters, while that based on Type II nets was generally slightly lower. Zooplankton biomass in the Bohai coastal waters was generally slightly higher than that in the North Yellow Sea coastal waters, with the most pronounced difference in autumn. The diversity index (based on Type I nets) in the Bohai coastal waters decreased slightly in autumn, whereas the richness index (based on Type I nets) in the North Yellow Sea coastal waters increased in autumn. The differences in temperature, salinity, and suspended solids between the two regions were highly significant (P＜0.001). Temperature, salinity, and dissolved oxygen were the main environmental factors affecting the zooplankton community structure in both areas. The results of this study provide a reference for ecosystem conservation in the Liaoning coastal waters of the Bohai Sea and the North Yellow Sea.