The invention provides a method for co-producing high-purity heparin sodium and dermatan sulfate from pig lungs. According to the method, the pig lungs are adopted as a raw material for producing high-purity heparin sodium and high-purity dermatan sulfate through enzymolysis, ion exchange, classified elution, concentration and ethanol precipitation. Specifically, the method comprises the steps of obtaining two steps of eluate through substep elution with ion exchange, removing salt and concentrating by using an ultrafiltration method, and further performing alcohol precipitation, thereby obtaining the heparin sodium and dermatan sulfate. In elution of ion exchange resin, a gradient sodium chloride solution is adopted for elution, so that heparin sodium and dermatan sulfate can be separated in eluate of different concentrations, the separation of heparin sodium from dermatan sulfate is achieved, the purity of heparin sodium and dermatan sulfate is respectively improved, the titer of heparin sodium and dermatan sulfate is also improved, and the purity, the titer and the optical rotation of heparin sodium and dermatan sulfate all meet the requirements of a pharmacopeia. The method is simple in process, low in cost and high in yield, and the economic benefits of product can be greatly increased.