To improve brittleness and optimize interface of glass-fiber/PVC composites, reinforcing and toughening technologies for glass-fiber/PVC composites were studied. Influences of glass-fiber and diallyl orthophthalate(DAOP) resin on their mechanical properties were observed. Diallyl orthophthalate(DAOP) resin was blended with PVC in various weight ratios by melt compounding. The compatibility between diallyl orthophthalate(DAOP) resin and PVC resin was analysed by measuring the impact toughness, tensile strength and bending strength. The results clarified that each mechanical properties improved, in addition to,SEM images show that the interface of glass-fiber/PVC composites added with DAOP was much closer , PVC resin surrounds completely the glass-fiber.