Abstract: A large amount of by-product-Neutrase could be accumulated during the liquid state fermentation of Bacillus subtilis AS 1.398 to produce antioxidant peptides with peanut meal as raw material. The results of single factor investigations and central composite design showed that, the optimum conditions to produce antioxidant peptides and Neutrase at the same time were inoculation amount of 1% (v/v) , natural pH, fermentation temperature of 34℃, fermentation time of 71 h. Under these conditions, the DPPH radical scavenging ability of fermentation liquid predicted was 81.51% and the activity of Neurtase was 600U/mL.