To quickly monitor and evaluate the prestress loss of Prestressed CFRP plate bridge in the early and late stage of reinforcement, a new distributed monitoring method is adopted to derive the long gauge strain numerical solution method of the concrete at the bottom of the beam after the end anchor is fully bonded with prestressed CFRP plate. On this basis, the prestress loss monitoring and evaluation indexes of static and dynamic prestressed CFRP plate are proposed; Then, through numerical examples, a three-dimensional numerical analysis model of multi piece small box girder strengthened with refined prestressed CFRP plate is established to study the influence of different vehicle parameters and different prestressed reinforcement levels on the accuracy of the static and dynamic prestress loss evaluation method. The results show that the error of static prestress loss evaluation method is less than 2.0%, and the error of dynamic prestress loss evaluation method is less than 2.8%, which proves the accuracy and theoretical feasibility of the proposed method.