The whitefish, Erythroculter ilishaeformis (Bleeker), is one of the important econmical fishes in the Danjiangkou Reservoir. This paper deals with the age growth, mortality of the whitefish as well as its harmfulness to the fingerlings of silver and bighead carps. In addition, population dynamics and rational exploitation of the fish are also discussed. The main technical calculation and chart are computationally processed by adoption of Schaefer and Beverton-Holt models. The results show:1. The growth of the whitefish in Danjiangkou Reservoir corresponds with von Bertalanffy's growth equations: The turning point of body weight and growth is at 3.4110 years.2. In Danjiangkou Reservoir, the fishing mortality coefficient F is 0.1050, the total mortality coefficient Z is 0.5129, and the natural mortality M is 0.4079.3. According to Schaefer model, the maximum sustainable yield (MSY) of the fish in Danjiangkou Reservoir is 113210 Kg, and the optimal fishing effort (F_msy) is 458164 Kg/day,T.4. When body length of the whitefish is from 366.7 to 395.5 mm, it would swollow the silver carp of 116.6 to 132.1 mm in length and bighead of 94.4 to 132.1 mm. If the first capture age of the whitefish is about 2.5 years (with body length of 400 mm and body weight of 900 g and mesh of gill net of 100-110mm), it would do no harm to the silver and bighead carps, for they are 167 and 183 mm in length respectively.5. If the age at first capture remains 2.5, the yield of whitefish will be 2.65 times as much as that at present, with the fishing Ievel F is 0.2.