An optimization of parameters in fermentation process of soybean protein by Bacillus subtitles 1398 and antioxidant activity of fermented peptides were studied.With the soybean peptides content and average peptide chain length as index,through single-factor and orthogonally experiment of additive amount of sucrose and water,inoculum dose,fermentation temperature and time,the optimal fermentation methods were obtained under the conditions of 0.5% of sucrose,2.0% of inoculum dose,60% of water,32℃ of fermentation temperature,and 32h of fermentation time.Under the optimized fermentation conditions,peptides content reached 252.95 mg/g.After preliminary purification,The inhibition rate to DPPH·,O2-· and ·OH of fermented peptides increased 119.53%,26.02% and 65.56% to merchant peptides,respectively.The result indicated that fermentation process was helpful for improving peptides content and antioxidant activity of hydrolyzed protein.