The feeding selectivity of Sagitta crassa, some ecological factors effect to the feeding rate and their diurnal feeding rhythm were experimentally studied in this paper. From the results, Sagitta crassa choose Moina mongolica first, second is Calanida, third comes Harpacticoide and never feed on Brachionus plicatilis. There were significant effects of food density. temperature and salinity on the feeding rate of Sagitta crassa. The relational formulas respectively are（1）Y=-0.0394X²+1.5861X-4.0500(R²=0.9235)（2）Y=-0.0514X²+1.3238X+7.3833(R²=0.9510)，（3）Y=-0.0275X²+1.3992X-6.3571(R^2=0.9041).The optimum food dencity for feeding was 100 ind·L^-1 Moina(15～20 mg·L^-1 biomass) In which the feeding rate was 11.9 ind·d^-1 Moina. The optimum temperature of water for feeding was 12.9 ℃ in which the feeding rate was 15.9 ind·d^-1 Moina. The optimum salinity for feeding was 25.4S in which the feeing rate was 11.4 ind·d^-1 Moina. There was more intense grazing behaviors of Sagitta crassa at night or slight light .The feeding rate of Sagitta crassa were minimum 8:00-12:00 and maximum 16:00-20:00.