There are many studies to reduce the plasma protein adsorption and to improve the blood compatibility. We already knew the PEG-rich surface give non-adhesive property to proteins. So surface modification by grafting a hydrophilic segment was often used. And in many situations, mechanical performance as well as biocompatibility is very important factor in medical application. So in this study, we polymerized 4-arm shape PLGA using co-initiator which has 4 hydroxyl group. To improve biocompatibility and control mechanical strength, we prepared blend film just mixing those two synthesized polymers with various ratio. mPEG gives the hydrophilic properties to the film surface and 4-arm shape PLGA polymer gives the mechanical strength to the film.