The behaviour of Modular GFRP(Glass Fiber Reinforced Polymers) decks for use in deteriorated bridge decks replacement are investigated experimentally in this study. As for the performance evaluation of bridge decks, experimental studies on the 3 test specimens with 1/5 scale of full size were carried out. Three specimens were sandwich plates with box tube cores. The constituents of bridge decks were glass fiber preforms and epoxy resin. The experimental results of all the specimens were summarized for maximum strength, stiffness and deformation capacity. A finite element analyses were compared to verify validity of experimental results.