The thermal denaturalization was applied to extract superoxide dismutase from porcine blood. On the basis of single-factor experiments, technological paraments were optimized by Box-Behnken central combination design and response surface methodology (RSM) with the specific activity of SOD as index. The crude enzyme was extracted by ethanol-chloroform and acetone, then purified by Sephadex G-100 gel column chromatography．The purified superoxide dismutase was identified by SDS-PAGE. The results showed that the specific activity of enzyme was significantly affected by bath temperature and copper sulfate content. The optimum conditions were bath temperature 66℃, bath time 25min and copper sulfate 3.10%，under which the special activity of crude enzyme was 167.74?0.38 U/mg. After purification, the special activity was increased to 6594.55?16.20 U/mg, with recovery rate of 62.15?0.02%. The purification of the enzyme was analyzed by polyacrylamide gel electrophoresis and the purified enzyme reached electrophoresis level.