Based on the water quality monitoring data and zooplankton survey data of 8 state-controlled monitoring points in Chaohu Lake area,the diversity index of the zooplankton community structure was analyzed and the water quality was assessed. The zooplankton density was also analyzed with cluster analysis method. The results showed that 41 species (genera) of zooplankton were identified in three investigations, and rotifers, cladocerans and copepods were the main groups. The Shannon-Wiener diversity index in the monitoring points of Chaohu Lake did not change significantly. The Margalef richness index was greater in 2020 than that in 2019, greater in the spring than that in the autumn, and slightly greater in the eastern lake than that in the western lake. Combined with the results of zooplankton diversity index analysis,water quality physical and chemical factors assessment, it was concludedthat the water quality of Chaohu Lake was in the state of mild-moderate pollution. The cluster analysis results showed that the water quality and zooplankton community structure in the monitoring points, except the middle monitoring point of eastern lake, had little difference.