The technology for extracting anthocyanins of black soybean seed coat was optimized by quadric regression orthogonal rotary tests. The results showed that the optimum extraction parameters were as follows: temperature 60℃, time 1 h, ethanol concentration 60%, the ratio of black soybean seed coat mass to ethanol volume 1∶40. It also showed that the most significant (P<0.01) correlations existed between total antioxidant capacity and anthocyanins contents. Moreover, the scavenging free radical capacity of anthocyanins in black soybean seed coat to OH·, O^-₂· and DPPH· was 1.6 times, 2.2 times and 1.4 times as large as that of Vitamin C, respectively.