Abstract: The spatial and seasonal distribution of zooplankton were examined in the Liaohe estuary in August (summer) 2013, October (autumn) 2013, and May (spring) 2014.The zooplankton species showed an obvious seasonal variation pattern, with the alternation rate of 40.91% from summer to autumn and 35.29% from autumn to spring.The most dominant species of zooplankton was Paracalanus parvus in summer, while it was Acartia bifilosa in spring and autumn.The total species number of zooplankton was significantly higher in summer than in spring and autumn although the species number of the copepoda varied little between 13 and 14 in different seasons.The increased group number of merozooplankton which accounted for 47.62% of the total species number of zooplankton explained the highest species number in summer.The individual number of zooplankton was highest in spring(6.4±1.3)×10⁴ ind./m³ and lowest in autumn(5.5±0.6)×10³ind./m³.Both the Shannon-Weaver index and Pielou index was higher in summer than in spring and summer.The Sperman analysis showed that there was a significant positive relationship between the spatial distribution of zooplankton diversity and salinity, but a significant negative relationship between zooplankton diversity and DIN and DIP.A significant negative relationship was found between the abundance of the indicator species Pseudodiaptomus poplesia and salinity, but a significant positive relationship between its abundance and DIN and DIP.This study is of significance for the ecological monitoring and government in Chinese estuaries.