The reinforced RC girder with external prestress is applied more and more widely. Reinforcement of the girder is influenced by various factors, among which the concrete intensity degree and the prestress degree are mainly analyzed through the finite element software ABAQUS to learn their influence on the anti-bending bearing capacity of the externally reinforced RC simply supported beam. Since the reinforcement stresses of RC girder (regular reinforced concrete beam) are far less than the maximum intensity of the reinforcing steel bar, the concrete in the pulled area cracks, which causes the stiffness of constructional elements to decrease, deform and expand so that the elements become useless before it is damaged. External prestress can effectively improve such defect of the RC girder, and a great deal of research has been carried out. Due to the experimental boundedness and discreteness, large general finite element software ABAQUS is adopted to analyze the anti-bending bearing capacity of the externally reinforced RC girder, which is based on the size of experimental constructional elements in literature.