An antifouling surface is highly desirable for many biomedical applications. In this study, poly(vinyl chloride) (PVC) films were endowed with the improved properties of resisting nonspecific protein adsorption and platelet adhesion simply through being coated with a kind of mixed‐charge zwitterionic polymer, poly(3‐sulfopropyl methacrylate–methacrylatoethyl trimethyl ammonium chloride–glycidyl methacrylate) (PSTG), with random moieties of negatively charged 3‐sulfopropyl methacrylate potassium, positively charged [2‐(methacryloyloxy)‐ethyl] trimethylammonium chloride, and glycidyl methacrylate. The PSTG‐grafted PVC films were formed by the simple immersion of an amino‐functionalized PVC film into a PSTG solution. A grafting density of 220.846508g/cmof PSTG4‐grafted PVC film was successfully obtained. The PSTG4‐grafted PVC film showed a lower contact angle (37.565°) than the ungrafted PVC film (98.365°). The in vitro protein adsorption results show that the bovine serum albumin adsorption amount decreased 6.726508g/cmin the case of the PSTG4‐grafted PVC film, whereas that on the ungrafted PVC film was 28.546508g/cm. So, PSTG‐grafted PVC films could be promising materials for medical devices.