In this study, we used a UV radiation grafting method to modify the surface of the biomaterial polycarbonateurethane (PCU). Hydrophilic poly(ethylene glycol) monoacrylate (PEGMA; number-average molecular weight = 526) as a macromolecular monomer was grafted onto the PCU surface by UV photopolymerization. The Fourier transform infrared and X-ray photoelectron spectroscopy results of the graft-modified PCU confirmed poly[poly(ethylene glycol) monoacrylate] block grafting onto the surface. We investigated the effects of the reaction temperature, macromolecular monomer concentration, UV irradiation time, and photoinitiator concentration on the grafting density (GD) in detail. Furthermore, we investigated the effects of GD under various process conditions on the water uptake and water contact angle. The modified materials had a high water uptake and low water contact angle, which indicated that the hydrophilicity of the PCU surface was improved significantly by the introduction of the hydrophilic poly(ethylene glycol) blocks on the surface. The anticoagulant properties of the material might also have been improved. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3717-3727, 2011