Abstract: This study was conducted to determine the optimal dietary thiamine requirement of juvenile blunt snout bream (Megalobrama amblycephala) on the basis of growth parameters, hepatic thiamine contents and plasma biochemical indexes. 720 fishesaverage initial weight:(0.30±0.01) g were fed six isonitrogenous and isoenergetic diets containing different thiamine levels (0, 0.51, 0.98, 1.59, 2.13and 2.68 mg/kg) 3 times daily for 8 weeks, respectively. Each diet was tested in four replicates, and each replicate holds 30 fish. The results showed that both the weight gain and specific growth rate of fish at 0.98, 1.59, 2.13 and 2.68 mg/kg groups were significantly higher than the control group (P < 0.05). Survival rate increased significantly as dietary thiamin levels increased from 0 to 2.13 mg/kg (P < 0.05). Plasma glucose level decreased significantly (P < 0.05) as dietary thiamine levels increased from 0 to 1.59 mg/kg, but it increased significantly (P < 0.05) with further increased thiamine levels. The addition of thiamine except 0.51 mg/kg group significantly increased plasma pyruvate level (P < 0.05). On the basis of the broken-line analysis of weight gain rate and hepatic thiamin contents, the optimal dietary thiamin requirement of juvenile blunt snout bream was 1.48 and 1.84 mg/kg, respectively.