We carried out this study from December 2002 to November 2003. The three collections stations and eight sampling spots are located respectively at Pihu, Paohu Suspension Bridge and band the water-gaining outlets of Baushan Reservoir. Vertical tower sampling collection is done once a month with 55µm -mesh size zooplankton net. The collected samples are brought back to the laboratory, numbered, and categorized. Nine species of zooplanktons (浮游動物), which can be categorized into six families of three orders in the classes of Rotifera(輪蟲綱) and Crustacea(甲殼綱)(including Cladocera, Calanoida, Cyclopoida), are found. The average density of zooplanktons in Baushan Reservoir in the 12-month period is 1.29*105 ind./m3. Among the four seasons, the highest density occurs in winter（8.61*105 ind./m3）. No obvious difference is found as to the density of the three testing locations. The appearing frequency of Rotifers(輪蟲)（7.27*105 ind./m3）is the highest of the discussed zooplanktons. That of Nauplius （4.22*105 ind./m3） goes next.
