Using metabolic flux balance model , the metabolic flux balance of L- v aline synthesis was established in this paper by material balances and linear p rogramming method. The analysis results indicate that 62.8% metabolic flux ent er ed EMP pathway and 38.2% metabolic flux entered the HMP pathway. And only 9.2 % c arbon entered the TCA cycle. But comparing to the optimal flux distributions of 92.31, the production of L-valine should be improved from the genetic manipula ti on and fermentation control through reducing byproduct of amino acid and decreas ing the metabolic flux.