Abstract: Based on the nonlinear dynamics model of an inextensional beam on elastic foundation, the 3rd superharmonic resonance of the beam subjected to the lateral harmonic excitation was investigated, and the effects of main parameters on the dynamic characteristic of the beam is analyzed. Applying the method of multiple scales, the frequency-response equation of the 3rd superharmonic resonance of the beam was obtained. Moreover, the frequency-response curves of the beam were drawn, and the effects of the foundation models, Winkler parameter, excitation amplitude and boundary conditions on the dynamic response of the beam were studied. The numerical results showed that the second elastic layer included in the three-parameter foundation model promoted the increase of the softening characteristic of the dynamic response, and this foundation model enhanced the nonlinear characteristic of the beam. The excitation amplitude had a certain influence on the dynamic characteristic of the 3rd superharmonic resonance of the beam, which causes the change of the initial drift of the backbone curve.