The best processing conditions of extracting total flavonoids in bitter bean seed's dregs residues were optimized by the orthogonal experiment method, and its Antioxidation. The best optimum processing conditions is: adding 25 fold amount of 70% alcohol and refluxing at 60 ℃ 2 times with 30 min each time. The extraction rate is 2.56%. The flavonoids had better scavenging ability of O2-·, ·OH, DPPH· free radical.