Hanasi Lake, located in Buerjin County, Aertai Region, Xinjiang Province, 48°43'-48°54'N, 86°59'-87°09'E, has an area of 45km², average depth 120.1 m. and maximum depth 188.5 m, belonging to a tectonic-glacial deposit dam lake formed by glacial erosion. Since 1985, it has become famous for its discovering the "big red fish" (Hue ho taimen (Pallas)).Hanasi Lake was surveyed twice, in Aug. 1987 and July 1988. According to the analysis of samples, 21 speceis of zooplankton have been identified, among which, 1 species belongs to Protozoa, 11 to Rotifera, 6 to Cladocera and 3 to Copepoda. The average amount of zooplankton is 60.7 ind./L and average biomass is 0.6499 rag/L. In addition, this paper deals with the characters of horizontal and perpendicular distributions for zooplankton, and estimates the amount which acts as the bait for fishes. All these may help discover the “raddle” of the “big red fish”.