Serum albumin, which is manufactured by the liver and is the protein of the highest concentration in plasma, can also be regarded as a naturally occurring and highly specific functional biopolymer. In this study, polyethersulfone (PES) membrane was modified by bovine serum albumin (BSA) with two methods. In the first methods, BSA was grafted to an acrylic acid (AA)-N-vinyl pyrrolidone (NVP) copolymer to form a biologic macromolecular hybrid polymer. The copolymer was synthesized in water solution and characterized by FTIR, which showed that AA was successfully copolymerized with NVP. The hybrid copolymer was also characterized by FTIR, and the BSA grafting ratio was calculated. The hybrid copolymer had potential use in the modification of polyethersulfone (PES) and other material membrane by blending technique. As for the second methods, PES membrane was modified by blending with the copolymer of acrylic acid (AA) and N-vinyl pyrrolidone (VP), followed by grafting BSA on the surface. The copolymer of VP and AA was successfully synthesized through UV irradiation. The copolymer and PES were dissolved in a mixed solvent of NMP and DMAC, and the membranes were prepared through a liquid-liquid phase separation technique. And then, BSA was grafted onto the surface of the membranes through the coupling of amino groups in the protein chains to the carboxyl groups in the VP-AA copolymer. The SEM results showed that PES had good miscibility with the copolymer and the membranes had typical asymmetricmembrane structure. XPS confirmed the existence of P(VP-AA) copolymer on the blended membrane surface and the existence of BSA after the grafting process. The amount of the grafted B SA on the surface of the membranes was determined. Water contact angles were determined and it was found that the advancing contact angles were mainly affected by the surface morphology of the membranes and increased after grafting with BSA. Protein adsorption, platelet adhesion and cytocompatibility of the BSA modified PES membranes were studied. The amounts of protein adsorbed from BSA, human plasma fibrinogen (FNG) and 10-fold diluted platelet poor plasma (PPP) were significantly decreased after the BSA was grafted onto the surface. According to the results of the circular dichroism (CD), the proteins kept more α-helix conformation when adsorbed on the modified membranes than on the pure PES. The number of adhered platelets was reduced and change in the morphology of adherent platelets was also suppressed by the modification with the BSA. The SEM morphological observation of the cells and the MTT assay demonstrated that the BSA grafted onto the PES membrane surface promoted the endothelial cells adhesion and proliferation. Therefore, the BSA grafting PES membranes, which possess both the good blood compatibility and cytocompatibility, is a promising biomaterial that may have potential use in blood contacting apparatus and many other artificial organs.