Carbon fiber reinforced polymer (CFRP) plates are commonly used to increase the ultimate strength of concrete structures in flexure. CFRP plates are also an effective means of rehabilitation and strengthening of concrete structures. In this paper an analysis model is presented for reinforced concrete beams externally reinforced with CFRP plates using finite elements method adopted by ANSYS. The finite element models using a smeared cracking approach for concrete and elastic shell elements for the CFRP plates. The results obtained from the ANSYS finite element analysis are compared with the experimental data for four beams with different conditions from research , three of which were externally strengthened with different amounts of CFRP reinforcement by changing the length of CFRP plate. The comparisons are made for load-deflection curves at mid-span over a span of 2000 mm, failure load and the optimum length of CFRP plate that can be used for flexural strengthening and achieve the adequate load – carrying capacity. The results obtained from the ANSYS finite element analysis were calculated at the same location for the experimental test of the beams. The accuracy of the finite element models is assessed by comparison with the experimental results, which are to be in good agreement. The load-deflection curves from the finite element analysis agree well with the experimental results in the linear range, but the finite elements results are slightly stiffer than that from the experimental results. The maximum difference in ultimate loads for all cases is 11%. The optimum length of CFRP plate equal to 83% of the full span length, obtained from the finite element analysis shows good agreement with that from the experimental test. Four additional models are used to find that 80% of the full span length is quite enough to be optimum length and beyond which the increase in the ultimate capacity is small and can be neglected to reduce the cost of the material.