A 70-day feeding trial was conducted to estimate the optimum requirement of dietary valine for juvenile grass carp using six isonitrogenous diets (32% protein) with peanut meal, casein, and gelatin as protein resource supplemented with six graded levels of coated valine (from 7.3 to 22.3 g/kg of dry diet). Each diet was randomly assigned to three replicates of 20 fish each with average weight of (9.5±0.3) g. The results showed that weight gain ratio (WGR), specific growth rate (SGR), protein efficiency ratio (PER), body composition, RNA/DNA ratio in muscle, digestive enzyme activity, alanine amino transferase (ALT) and aspartate amino transferase (AST) and glutamate dehydrogenase (GDH) activity in hepatopancreas and hematology were all significantly (P<0.05) affected by the dietary valine levels. WGR, SGR, PER and RNA/DNA ratio in muscle were significantly increased with valine level increasing from 7.3 to 16.3 g/kg of diet (P<0.05), and then decreased. Second-degree polynomial regression analysis for WGR, PER and RNA/DNA ratio in muscle indicated that the optimum requirements of dietary valine of juvenile grass carp were 15.6, 15.1 and 16.0 g/kg of diet (48.8, 47.2 and 50.0 g/kg of dietary protein), respectively.