The red pigment from the seed coats of red adzuki beans was extracted by soaking in water and separated by the pressure-driven membrane technology (microfiltration, nanofiltration, etc.), and the separation processes were also optimized. The results showed that the optimal extraction conditions of pigment from seed coats were as follows: the ratio of material to liquid (mass of seed coats: volume of water) at 1∶30 （g/mL）, extraction temperature 90 ℃, extraction time 90 min, and the color value of the extracts reached 7.53. The optimized membrane separation process was the combination of microfiltration (0.22 μm) and nanofiltration membrane (NF245), with the microfiltration pressure at 0.075 MPa the membrane flux speedat 12.47 L/(m²·h), and the pigment transmission rate at 87.16%; the optimal pressure for NF was 0.3 MPa, and the stable flux was 16.06 L/(m²·h). The content of pigment in the NF concentrate increased to 810.19 mg/L and the concentrations of total phenol, total sugar and protein were further reduced. The content of anthocyanin in the purified anthocyanin freeze-dried powder was （145.80±0.17） mg/g. The color value of the purified anthocyanin was 58.08±0.09, which was 2.41 times of that before purification.