Abstract: Single-factor test and orthogonal experiment was used to optimize fermentation condition of the Lactobacillus delbrueckii QS701 to prepare highly active angiotensin-I converting enzyme(ACE)inhibitory peptides. And the results showed the effect of these factors of angiotensin converting enzyme inhibitory active was the ratio of fermentation time>fermentation temperature>inoculum size. The optimum of fermentation conditions was inoculum size 3%,temperature 43℃,fermentation time 72 h,and the result of ACE inhibitory rate was 81.58%,so this fermentation condition used in to prepare highly active angiotensin-I converting enzyme(ACE)inhibitory peptides.