${gamma}$-APS (${gamma}$-aminopropyltriethoxysilane), one of the silane coupling agents, was used to treat glass fiber surfaces to modify the interphase between fiber and matrix. FT-lR (Fourier Transform Infrared) and XPS (X-ray Photoelectron Spectroscopy) were used to characterize functional groups and atoms, respectively, adsorbed on the fiber surface treated by ${gamma}$-APS. The adsorbed amount of ${gamma}$-APS on the fiber surface was measured as a function of concentration, pH, treatment time and treatment temperature. The single glass fiber treated at various treatment conditions was embedded between nylon 6 films to make a single fiber embedded specimen which was used to assess the interfacial shear strength by fragmentation test.