Poly(gamma-MPS-co-styrene), as a surface modifier of glass-fiber-reinforced polystyrene composite, was synthesized to improve the adhesion between glass fiber and polystyrene matrix. The copolymerization was carried out using AIBN as the initiator at 70 degrees C. The reactivity ratios of gamma-MPS and styrene were determined by the Finemann-Ross method. The result was r(1) (styrene) = 0.10, r(2) (gamma-MPS) = 0.86. Judging from these results, the copolymerization of gamma-MPS and styrene was azeotropic copolymerization and the synthesized copolymer was a random one. Thermal stability of the copolymer was improved as the content of silane in the copolymer was increased and the glass transition temperature decreased. The surface-modified glass fiber was investigated with Fourier transform infrared spectroscopy (FTIR). The glass fiber surface was effectively modified with the copolymer.