Abstract: Zooplankton plays an important role in regulating the structural balance of marine ecosystem. In order to study the distribution of zooplankton in Tianjin coastal waters and its relationship with the environmental factors, a survey was carried out at 16 monitoring sites in Tianjin coastal waters in September 2020. The biodiversity index was used to evaluate the zooplankton diversity, redundancy analysis (RDA) and principal components analysis (PCA) were used to analyze the relationship between zooplankton diversity and water environment factors as well as the main water environment impact factors in Tianjin coastal waters, respectively. The results showed that 18 species of zooplankton were identified and Copepods were the main group, which accounting for 50% of the total zooplankton, and the dominant species were Copepodite larva, Corycaeus affinis and Nauplius larva (Copepoda). Margalef richness index (D), Pielou evenness index (J), Simpson dominance index(C) and Shannon-Wiener diversity index (H') were 1.37, 0.71, 0.36 and 1.31, respectively. RDA showed that suspended solids (SS) was negatively correlated with total biomass, D, J and H', respectively. The concentration of active phosphate was positively correlated with J and H', while pH and salinity were negatively correlated with the C. The concentrations of chlorophyll a and ammonia were positively correlated with C and J. The content of dissolved oxygen was negatively correlated with C and total biomass, while that of petroleum was negatively correlated with C. PCA showed that the main water environment factors affecting zooplankton diversity distribution in Tianjin coastal waters were suspended matter, chlorophyll a and ammonia.ll a and ammonia.