This paper focuses on the characterization of flexural behavior of RC beams strengthened with Near-Surface Mounted (NSM) GFRP bars. Based on ABAQUS, the finite element model for the flexural behavior is established and the simulated results are compared with the test results. The parameters including the amount of GFRP bars, the embedment length of GFRP bars, the types of FRP bars, and the ratio of internal steel reinforcement in the beam for the flexural behavior are discussed. The simulated results show that there has a good agreement with the experiment results. The beams strengthened with NSM GFRP bars have a significant improvement in flexural stiffness and bending capacity. Further more, the analysis results on the parameters indicate that ultimate bearing capacity of the beam strengthened with NSM-GFRP bars gradually increases with the amount of FRP bars and the ratio of the longitudinal steel reinforcement. The mode of failure of the beam strengthened with the smaller embedment length of GFRP bars is not the rupture of GFRP bars. The different types of FRP bars have a great influence on the load-deflection curves of the beams.