According to the assumption of plane section deformation and considering the nonlinear properties of materials, the load-deflection relationship of prestressed CFRP reinforced concrete beams is calculated by the method of stepwise strain addition. The load-deflection curves of 5 prestressed CFRP reinforced concrete beams and 4 non-prestressed reinforced concrete beams are in good agreement with the experimental results. Based on the mechanical model, the nonlinear analysis of the secondary mechanical properties of the flexural members reinforced by prestressed CFRP is carried out, and the effects of the initial strain, section height and prestress on the flexural properties of the reinforced beams are studied. The results show that prestressing can effectively exert the high strength properties of carbon fiber, and the reinforcement effect of prestressed carbon fiber cloth under secondary stress is much better than that of non-prestressed carbon fiber cloth, which can effectively solve the problem of stress and strain lag under secondary stress.