The bearing capacity of members strengthened with prestressed carbon fiber reinforced plastic is improved significantly, however, the ductility of the members strengthened are reduced obviously. Moreover, no sign are observed before the failure and the failure process rapidly. The current study proposed a reinforcement method based on early-warning fuses theory to address this issue and took carbon fiber reinforced plastic as an example. First, it's necessary to determine the area of carbon fiber board and the application of prestressed in each part of the member (early-warning fuses part and load-bearing part). This needs to be determined by the basic safety reserve and the additional safety reserve of the carrying capacity, then the calculation formula are derived; second, designing six simulation beams and four test beams. Based on the comparison of the computation of the derived formula with the simulation and test results, the calculated values of the early-warning load agree well with the simulated and experimental values, and the calculated values of the ultimate load are less than the simulated and experimental values. This showed that the theoretical calculation method has high accuracy. In addition, various evaluation index prove that the members strengthened have sufficient reserves.