The use of glass-fiber-reinforced polymer (GFRP) bars in reinforced concrete (RC) structures has emerged as an alternative to traditional RC due to the corrosion of steel in aggressive environments. Although the number of analytical and experimental studies on RC beams with GFRP reinforcement has increased in recent decades, it is still lower than the number of such studies related to steel RC structures. This paper presents the experimental moment deflection relations of reinforced beam with spliced GFRP bars. Test variables were lab-spliced length of GFRP rebars. The development length was calculated according to the ACI 440 for GFRP rebars in concrete. A total of 6 concrete beams reinforced with steel and GFRP rebar tested. Three concrete beam reinforced with spliced GFRP rebars and 1 reference beams reinforced with non-spliced GFRP rebars were tested. All the specimens had a span of 4000mm, provided with 12.7mm nominal diameter steel and GFRP rebars. All test specimens were tested under 2-point loads so that the spliced region be subject to constant moment. The test results indicated that the modification factor of 1.6 and 1.75 is relatively sufficient for the bond development length of GFRP rebars archiving adequate tension lap splice length.