[en] Starch is added to polystyrene (PS) for the purpose of increasing degradability of PS. The use of compatibilizer can promote compatibility for PS/Starch blends. The most common form of compatibilizers is graft copolymers. In this work graft copolymerization of styrene onto gelatinized wheat starch by a mutual irradiation technique was carried out. Irradiation was done under γ-rays in nitrogen atmosphere and product was characterized by FTIR, DSC and SEM techniques. PS was blended with wheat starch using the addition of Starch-g-PS as the compatibilizer. Also similar blend without the presence of compatibilizer was prepared as control sample. Both of blends, PS/Starch-g-PS/Starch and PS/Starch, were tested by measuring the tensile properties, water absorption and microscopic observation of surface structure. The results showed that the presence of Starch-g-PS in blend lead to the improvement of miscibility and properties