Aiming at the problem that military bridge equipment is prone to accidents under the state of on-load, a certain type of wheeled impact bridge is taken as the research object to analyze the bridge span structure and the specified load. The finite element method is used to calculate the displacement, stress and deformation of the bridge span under f on-load. According to the calculation results, the deflection, displacement and stress are selected as the monitoring parameters, and the effective independence (EI) method based on modal assurance criteria (MAC) is used to optimize the sensor layout. The monitoring hardware system is constructed by wireless data transmission, and the hardware module box is designed. The host computer software is developed based on LabVIEW. The functions of data acquisition, data analysis, status display and safety warning are realized. The test results show that the monitoring system can effectively reflect the attitude information of the bridge span under on-load, and realize the early warning of accidents.