The standing crop of plankton and primary productivty of phytoplankton are surveyed in Sandaohe Reservoir, Hubei Province from April to October, 1990, The results show that there are 39 genera of phytoplankton, subordinate to 8 phyla, and 37 genera of Zooplankton, of which Protozoa, Rotifera, Cladocera and Copepoda account for 12, 13, 7 and 5 species respectively.The gross primary productivity of phytoplankton in the water column reaches 3.950 g O₂/m²·d in average in the period of April to October, 1990.The mean standing crop for phytoplankton and zooplankton is separately 1139 ind./mL, 2.085 mg/L and 1253 ind./L, 1.327 mg/L.The potential annual production of silver and bighead carps may raech to 15×10⁴ kg.The number of silver and bighead carps fingerlings (5 cm in length) to be stocked each year should be 78×10⁴ and 143×10⁴ respectively.