Abstract: To evaluate the water quality situation, this study investigated zooplankton species, density and biomass and the main water quality indexes like water temperature, conductivity, DO and pH in 12 cross-sections in the Wei River Basin in October of 2017 and June of 2018, respectively, using the biological diversity index method. 57 species of zooplankton species (11 species of protozoa, 33 species of rotifers, 7 species of cladocerans, 6 species of copepods) were identified, and the dominant species was Brachionus calyciflorus. During dry season, the density of zooplankton varied between 0.72—7.84 ind./L with the average density of (2.79±2.11) ind./L, and the biomass ranged from 0.38 to 6.15 mg/L with the average biomass of (2.31±2.64) mg/L. The diversity indices of Shannon-Wiener and Margalef were 1.07 and 0.69, respectively. The canonical correspondence analysis indicated that the community structure of zooplankton in the Wei River Basin was primarily affected by the water environment including temperature, DO, altitude and conductivity. During wet season, the density of zooplankton varied between 0—179.02 ind./L with an average density of (16.66±49.18) ind./L, and the biomass ranged 0—2448.12 mg/L with an average biomass of (243.96±673.78) mg/L. The diversity indices of Shannon-Wiener and Margalef were 0.78 and 1.15, respectivly. The water quality of Wei River in Beidao and Linjiacun was moderately polluted, and the water qualities in Weijiabao were heavy pollution, and in Xianyang, Lintong, Huaxian the water qualities were light pollution. The water quality of Jing River in Yangjiaping, Yuluoping and Zhangjiashan was moderately polluted. The water quality of Beiluo River in Liujiahe, Jiaokouhe and Zhuangtou was moderately polluted.