This paper presents the nonlinear finite element modeling of the global behavior for RC beam strengthened by externally epoxy bonded steel plates up to failure. In addition to the consideration of nonlinear behavior and cracking of concrete, the model involves interface element to capture not only the shear and normal stress concentration at the plate curtailment, but also the separation due to the exceeded peak shear and normal stress. The internal steel bar using truss element and the external steel plate using deformation theory of plastic have been confirmed by compare finite element solution with plastic theory. The proposed finite element solutions result in close correlation with experimental data available for RC beams strengthened by epoxy bonded steel plates with different thickness.