A feeding trial was conducted to evaluate the effects of dietary methionine levels on growth performance, body composition of GIFT(Oreochromis niloticus) [ initial body weight of(66.76±2.29) g].Six isonitrogenous(32.09% crude protein) and isoenergetic(17.82 kJ/g gross energy) semipurified diets were formulated with the graded methionine levels(0, 0.3%, 0.6%, 0.9%, 1.2% and 1.5% dry diet, respectively), using gelatin, fishmeal, peanut meal and crystalline amino acids mixtures as the main dietary protein sources.Amino acid pattern in diet is to simulate the amino acid pattern found in the whole body protein of GIFT except for methionine.The six trial diets were determined to contain methionine of 0.26%, 0.55%, 0.85%, 1.14%, 1.44% and 1.73% dry diet, respectively.Each diet was randomly assigned to triplicate groups of 25 fish and fed to apparent satiation by hand thrice daily(8:00, 13:00 and 16:00) for 60 days.The results showed that the weight gain rate(WGR), specific growth rate(SGR), protein efficiency ratio(PER) and protein deposition rate(PDR) initially increased with increasing dietary methionine levels, but then decreased.Conversely, the feed conversation ratio(FCR) first decreased and then increased.The WGR, SGR, PER were all the highest(361.91%, 2.73%/d and 2.53% respectively) when the dietary methionine level was 1.14%.At the same time, the FCR was the lowest(1.23).The PDR was the highest(47.22%) when the dietary methionine level was 1.44%.The hepatosomatic index(HSI) and viscerosomatic index(VSI) of GIFT first decreased with increasing dietary methionine levels, but then increased(P<0.05), yet the condition factor(CF) had no significant differences(P>0.05).The tendency of crude protein content in muscle was similar to WGR and SGR with increasing dietary methionine levels(P<0.05), while the crude lipid in muscle first increased with increasing dietary methionine levels and then leveled off.And there were no significant differences of crude protein in whole body, moisture and the ash in whole body and muscle(P>0.05).With the increase of dietary methionine level, the histidine, serine and cystine in muscle had no significant differences(P>0.05), at the same time, the all other amino acids contents, gross of essential amino acid(ΣEAA), gross of total amino acid(ΣTAA) in muscle first decreased, then increased.With the WGR, SGR, PER, PDR, FCR as evaluation indicators, quadratic regression analysis showed that the optimum dietary methionine level of GIFT was 1.13%-1.16% of diet(dry matter basis) or 3.52%-3.61% dietary protein with cystine level at 0.30%.