Abstract: The salangid fish Neosalanx taihuensis has become into a major export fish pfodect in Yunnan. In recent years, the accretion of Cultrichthys erythropterus population was supposed to be the major factor that had cause the salangid fish yield to drop down. The present investigation has revealed that the individuals of C. erythropterus smaller than 100mm SL feed mainly on Cladocera; individuals of 100-130mm SL feed mainly on Cladocera and shrimps (each accounting for about half of the food amout); individuals over 130mm SL feed mainly on shrimps as well as aquatic insects and little fishes (the aslangid fish has occurred only for 2 times, occurring frequency being 0.45%). Based on these results, it is concluded that C. erythropterus shows meager direct interference, and little indirect interference, on the salangid fish. These discoveries from the investigation have been included into the fishery management of Dianchi Lake.