This paper is disserted to the vibrations of the sandwich panels with pyramidal truss cores. Firstly, based on the Hamilton principle the governing equations of a sandwich panel with pyramidal truss cores are obtained and the eigenfrequencies of the sandwich panel is studied. Then the dynamic response of the sandwich subjected to uniformly distributed sinusoidal loading is studied. The influences of the sizes of the panel on the eigenfrequencies of the panel are discussed. The maximum deflections of the panels of equal mass subjected to the same loading are compared.