The construction monitoring characteristics of truss beam bridge reconstruction are analyzed by taking the reconstruction of Songpu Bridge as the background. The overall control idea of the construction monitoring of old bridge mainly based on the safety control of structure and supplemented by the adaptive control of new and old structures is established to study the relevant monitoring and control methods. Regarding the construction phase of the support replacement, the reaction force of the support and the dynamic characteristics of the main truss are identified, and are compared with the theoretical calculation results to verify and evaluate the overall technical status of structure. In addition, the working mode of monitoring data and information interaction platform based on "Internet+" is developed and applied, which provides the theoretical referring basis for the construction monitoring of the similar bridges at home and abroad.