Abstract: The feeding intensity of silver carp and bighead varied with season under natural condition in Donghu Lake. With the increase in temperature, the fullness index of both fishes increases, and vice versa. The maximum feeding intensity appears in summer, and the minimum in winter.The evacuation rate of both fishes was determined under experimental condition. The relationships between the period of food passing through the fish intestine(Yp, hour)and water temperature(Xt, ℃)are: Silver carp: Yp= 270.63Xt0.6408 Bighead: Yp= 280.46 Xt0.6642According to the modified Bajkov's formula D = C(24·A)/n), the estimates of the daily ration of the two fishes were obtained. The relationships between the daily ration of the fish(YD,% wet weight of fish)and water temperature(Xt, ℃)are: Silver carp: YD= 0.268 3e0.1503xtBighead: YD= 0.0075 Xt2.2715The monthly and annual rations of both fishes were calculated. The annual consumption of natural food by silver carp and bighead was 18.924 kg and 17.39 kg, respectively. The food quotients are 18.02 for silver carp and 13.38 for bighead.