To improve the blood-compatibility of polyurethane, the co-solvent of tetrahydrofuran and water, a new solvent system for blending polyurethane and heparin, was proposed. After solvent casting, heparin was blended in a polyurethane film. The ATRFTIR was used to analyze the surface chemical element and the contact angle was measured to investigate the hydrophilicity of the surface of the PUs. As the amount of heparin increased, the surface hydrophilicity was increased and all the clot times exceeded the measurement limit of the clot detection instrument when the heparin loaded on the polyurethane films was 3%, 5% and 7%. After the films were immersed in the phosphate buffered saline for 30 days, the activated partial thromboplastin time and thrombin time still exceeded the measurement limit of the clot detection instrument.