Abstract: Three experiments were carried out, each dealing with six aliquots of 60-100 grasscarp fingerlings which weighed 2.4-8.0 g, Each aliquot was assigned to one of six dif-ferent dietary protein levels ranging 0.44-50.46%, with the daily feed allowance ap-proximated 5-9% the body weight of the fish, and kept in a 2.4M3 concrete tank at26-30.5℃ for 21-27 days. These experiments were aimed at determining the optimallevel of dietary protein for the optimum growth of juvenile grass carp. The sourcesof protein used were casein and dried meal of silver carp muscle. The optimal proteinlevel of the diet, determined by both methods of polynominal regression and paraboliccurve, was found to be 22.77-27.66%. The protein efficiency ratio decreased with theincrease in protein content of the diet according to the formula Y=29.2786-0.5296 X.At the optimal protein level, the protein efficiency ratio was defined as 14.72-17.11 %.