In our recent study, an ABA amphiphilic triblock copolymer poly(vinyl pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinylpyrrolidone) (PVP-b-PMMA-b-PVP) was synthesized and directly blended with polyethersulfone (PES) to prepare membranes.To further investigate the effects of surface energy and miscibility on the near-surface composition profile of the membranes,evaporation membrane and phase inversion membrane of PES/PVP-b-PMMA-b-PVP were prepared by evaporating the solvent in a vacuum oven, and by a liquid–liquid phase separation technique, respectively. The surface composition and morphology of the membranes were investigated using XPS and tapping mode atomic force microscopy, and the surface segregations of the membranes were compared and discussed. For the evaporation membrane, PVP blocks were buried below the lower surface energy PMMA blocks and PES substrate at the airside surface. For the phase inversion membrane, however, the hydrophilicity of PVP blocks were the biggest driving force because of the high speed exchange between water and solvent, and present at the membrane surface. Thus, the modified PES membrane prepared by using phase inversion method has a layer of PVP block brushes on its surface and has the better anticoagulant property, which might improve the blood compatibility of the membrane and has potential to be used in blood purification