Abstract: The fermentation conditions of the mold producing valonia tannin hydrolase were studied.The optimum fermentation conditions were 5.0 g/L valonia tannin,20 g/L sucrose,6.0 g/L peptone,100 mL culture medium in a 250 mL cone bottle,initial pH 5.0,30 ℃ and 120 r/min shaking for 48 h.The hydrolase was the most stable at pH 4.0～5.0 and 30 ℃.