The plankton and hydrochemistry are surveyed in Lushui Reservoir. Hubei Province from January to December. 1991. The results show that there are 118 genera of phytoplanktion and 198 species of zooplankton. The average density of phytoplankton and zooplankton is 3. 1449 ×10~5 cell/L and 2323. 8 ind. /L respectively and the average biomass 1. 937 mg/L and 1. 4837 mg/L respectively, in which Cryptophyta, Bacillariophyta. Cladocera predominated. The species composition and standing crop of plankton vary with different regions and seasons. The mean gross primary productivity of phytoplankton reaches 3. 4gO2/(m2 ?d), but phosphate is still a limited element to it. According to the characteristics of plankton and the data of hydro-chemistry. Lushui Reservoir belongs to mesotrophic type. The effects of environmental factors on the plankton of Lushui Reservoir are also discussed in this paper.