Feeding experiments were conducted with protein diets(PD)and proteinfree diets(FPD) for Hucho taimen（6.8-7.3 g）, the diets(PD) was prepared by casein and gelatin as protein source with high biological values. The whole body amino acid composition was determined at the beginning and the end of the study. The requirements of Hucho taimen for essential amino acids(EAA) were determined based on the daily increment and daily maintenance requirement of each EAA in fish body. Fish were raised in tanks. There were 2 diets, each diet was randomly assigned to triplicate groups of 25 fish. During the experiment, the water temperature fluctuated from 23 ℃ to 25 ℃, and the dissolved oxygen was 6.4 mg/L to 7.5 mg/L. The experiment was conducted for 28 days. Compared with the FPD fish, the survival rate, the feed coefficient rate, the weight gain and crude lipid were increased significantly(P<0.05).The daily maintenance requirement of EAA(except trytophan) accounted for 20% to 30% of the sum of daily increment and daily maintenance requirement, and accounting for 54.52% of tryptophan. So the daily maintenance requirement of EAA can not be ignored. The minimum requirements of EAA needed to satisfy the requirements of Hucho taimen［g/(100 g body weight)/d］ were: Threonine 0.040, Valine 0.041, Methionine 0.027, Isoleuline 0.034, Leucine 0.067, Phenylalanine 0.035, Lysine 0.068, Histidine 0.110, Arginine 0.050. When dietary protein level was 42％, the minimum contents of EAA in the dietary(g/kg diet) were as follows: Threonine 4.17, Valine 4.24, Methionine 2.84, Isoleuline 3.56, Leucine 6.99, Phenylalanine 3.64, Lysine 7.18, Histidine 11.53, Arginine 5.19 and Trytophan 0.76.