【Objective】Effects of dietary essential amino acid (EAA) balance relativity on growth, digestion and metabolism of protein of Cyprinus carp were investigated.【Method】Contral diet (33% mass fraction of protein) was formulated with fish meal as protein source.Six isoenergetic (17 MJ·kg^-1) and isonitrogen (31% mass fraction of protein) diets were formulated with plant protein source at different levels of EAA balance relativity by adding different levels of methionine and lysine. Cyprinus carp with the initial body mass(53.29±1.64) g was fed with seven diets at different levels of EAA balance relativity［0.764 9(control group), 0.704 8(group 1), 0.722 0(group 2), 0.737 0(group 3), 0.759 1(group 4), 0.778 0(group 5) and 0.800 8(group 6)］for 8 weeks.【Result and conclusion】The mass gain rate and specific growth rate increased with the increasing EAA balance relativity, thus reaching the 0.778 0(group 5),which was significantly higher than those of group 1,group 2 and group 3(P＜0.05). There was no significant difference between group 5 and the control group(P＞0.05), and the feed efficiency showed a similar trend.The protein efficiency increased with the increasing EAA balance relativity, thus reaching 0.759 1(group 4),which was significantly higher than those of group 1, group 2 and group 3 (P＜0.05), and no significant difference was observed between group 4 and the control group(P＞0.05).Compared with the control group,the hepatopancreas protease specific activity and the activity of alanine aminotransferase had no significant difference (P＞0.05)when the EAA balance relativity was 0.759 1(group 4), and the hepatopancreas protease specific activity was significantly higher than those of group 1, group 2 and group 3(P＜0.05).When the EAA balance relativity was 0.759 1(group 4), the activity of aspartate aminotransferase had no significant difference compared with the control group(P＞0.05).When the EAA balance relativity was improved to 0.759 1(group 4),the total serum protein showed no significant difference between group 4 and the control group(P＞0.05), but the serum albumin had no significant difference between group 3 and the control group(P＞0.05).Under the current condition, the plant protein source feed is supplemented with the methionine and lysine to regulate the EAA balance relativity, reaching 0.759 1, which can promote the growth, digestion and metabolism of protein of C. carp, thus decreasing the content of dietary protein and the cost of feed.