This paper reports the results of comparative study on the population ecology of asian smelt(Hypomesus transpacificus nipponesis)and large icefish(Protosalanx hyalocranius)in Shuifeng Reservoir from October 1998 to November 2000, which include the behavior of feeding, growth, reprcduction and population structure.The asian smelt is an omnivorous fish which feeds mainly on zooplankton.The eggs of same spcies in spawning period were preyed upon, with a frequency of occurrence of 42.9%.It also fed on eggs of large icefish in winter with a frequency of occurrence of 2.8%.The regression equation of body weight(W)and body length(L)was W=1.176×10^-6L^3.556.The dispersed degree of body length and body weight in population structure was small.The large icefish feeds mainly on zooplankton in early life and adult fish mainly feeds on small fish and shrimp.The frequency of occurrence of asian smelt in the food was 6.9%-9.6%.The regression equation of body weight and body length was W=4.482×10^-6L^3.004.The dispersed degree of body length and body weight was large which showing difference of individual growth.