Abstract: In this paper, the method of identification of moving time dependent loads from bridge responses based on Euler beam vibration theory is introduced. The modal displacements of the beam were identified from the deflections on strains of the beam. The modal velocities and accelerations of the beam were calculated with central difference method. The moving forces were identified with the least square method based on the modal coordinate equation of the beam. The influence of test error, load spaces and bridge span on the identification are discussed.