Manufacturing biomedical flexible Poly (vinyl chloride) (PVC) products requires the nontoxic plasticizers and the biocompatibility. In this study, a series of methoxylated poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer (MPEG-PCL) with variety molecule weight were synthesized by ring-opening polymerization of epsilon-caprolactone with methoxylated poly(ethylene glycol) (MPEG) as macroinitiator. The structure of the block copolymers was characterized utilizing FTIR, NMR, SEC, and DSC. Because the compatibility between PVC and PCL, a series of MPEG-PCL/PVC blends were prepared. The results of DSC and mechanical properties of blends show that PVC could be plasticized with MPEG-PCL and the diblock copolymer is probably to be used as a polymeric plasticizer for PVC. Moreover, the water contact angle results indicated that MPEG-PCL also provided PVC the hydrophilic properties. At the same time, it was found that the blends showed favorable anticoagulation property which can probably exploit the potential application of the blends in the biomedical areas. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 107-115, 2009