The free vibration and nonlinear forced vibration of the sandwich beam with pyramidal truss core were investigated. The zig?zag theory was used to derive the nonlinear dynamic equation for the truss core sandwich beam. The natural frequencies of the sandwich beam were also calculated and verified. The effects of strut radius, inclination angle and core height on the natural frequencies of the sandwich beam were then analyzed. Meanwhile, the nonlinear frequency responses of the sandwich beam under different excitation amplitudes and with different structural parameters were studied. The results show that the natural frequencies of the sandwich beam increased and then decreased with the increase of three structural parameters. In addition, the structural parameters of the truss core exhibited complicated effects on nonlinear responses of the sandwich beam.