Abstarct: Today using fiber-reinforced polymers (FRP) is one of the most practical methods to strengthen members of reinforced concretes. FRP’s easy applicability due to its low weight, high tensile strength and anti-corrosive properties has made it a suitable substitute for traditional materials and conventional methods. During the recent years, retrofitting of reinforced concrete structures by bonding the FRP laminates to the outer surfaces of members has growed significantly. We have tried to study the flexural performance of strengthened reinforced concrete beams using ABAQUS software. First, a numerical model was simulated from a non-strengthened RC beam as a control beam and a pre-stressed laminated CFRP-strengthened concrete beam (Xue et al experiment, 2008). The accuracy of this modeling was approved because there was a good coordination between the results of the numerical method and the results of the experimental samples. Using finite element analysis, we studied the effects of parameters such as tensile reinforcement ratio and CFRP laminate characteristics, such as their width, thickness and the degree of pre-stress, on the flexural behaviors of RC beams, afterwards. Analyzing the results showed, using pre-stressed CFRP laminates to strengthen RC beams, results in a significant increase in the stiffness and flexural capacity of the beams.