An experiment was conducted to determine the requirement of dietary vitamin B1 (thiamine, TN) for juvenile Litopenaeus vannamei. Semi-purified basal diets were formulated using vitamin-free casein, gelatin and fish meal as protein resources. Graded levels of TN were added to the basal diet which analytically contained 0.83, 19.70, 37.40, 50.80, 65.30, 94.20, 163.00 and 323.00 mg/kg diet, respectively. Each diet was fed into tanks of three replicates of shrimp (mean weight of (0.55±0.03) g) for 42 days. Results indicated that the specific growth rate (SGR) and feed efficiency of shrimp fed diets supplemented with thiamine were significantly higher than those of shrimp fed non-supplemented diet (0.83 mg/kg diet) (P<0.05). Shrimp fed 19.70～50.80 mg/kg diets had a significantly higher survival rate (P<0.05). There was no significant difference in body composition and hepatopancreatic amylase activity among the groups (P>0.05). The activity of serum transketolase (TKA) was the highest in shrimp fed 50.8 mg/kg diet, significantly higher than that of shrimp fed the non-supplemented diet. SGR and TKA in serum were found to be suitable indicators, and analysis of broken-line regression indicated that the dietary vitamin B1 requirement of Litopenaeus vannamei was estimated to be 23.90 and 23.70 mg/kg diet, respectively.［Chinese Journal of Animal Nutrition, 2010，22（4）:977-984］