Based on the modal superposition theory, the second order derivative of the modal coordination is firstly obtained from the acceleration of the bridge at several sections. The inertia force of the bridge is then expressed as distributed load by means of the d′Alembertian theory. Using the bending moment influence line of the bridge, the relationships between the moving load and the moment is proposed. The moving force can be obtained at any time points through the developed formula. Case studies show that this proposed method performs high accuracy in identifying timevarying as well as constant moving force. Moreover, this method doesn′t need to deal with the illcondition due to matrix singularity, which makes it in high efficiency and appropriate for engineering application.