The carp fingerling was fed with formulated feed containting different protein quantities and various animal protein sources. Under the equal environmental condition and the same feeding rate，the gained weight rates and RNA，DNA contents of fish's muscle and liver were measured. The result showed:When feeding groups of A，B, and C were contained protein in 18. 17%，17. 86 0 oand 31. 56% respectively，and the average gained weight rates of each group were 106. 87%.94. 65%and 129. 48%.The mean feed coefficients were 2. 04，2. 30 and 1. 52，and RNA/DNA ratios were 2. 99，2. 90 and 4. 13 respectively. Moreover，RNA/DNA ratio is a very sensitive indicator in reflecting fish growth rate and protein content in the feed. Therefore，RNA/DNA ratio in the muscle can evaluate fish growth and the quality of the formulated feed.