Objective To improve the isolation effect of the pulmonary surfactant protein A. Methods We isolated and purified pig pulmonary surfactant protein A. The pig lungs were washed with saline. The mixture was centrifugalized and protein sediments were obtained. The sediments were isolated and purified by dialysis. We detected their biological activity by MTP-1 balance. Results The samples upon SDS/polyacrylamide gel electrophoresis showed that the molecular weight was 29.7 ×10 3 and the number of bands was reduced. When added to artificial phospholipids, its biological activity was enhanced ( P < 0.01 ). Conclusions The method of dialysis can effectively purify the pig pulmonary surfactant protein A. The method can also keep its biological activity well.