Abstract: Honeycomb structure has been widely used in transportation vehicles such as aircrafts, ships, high-speed train. The paper defines the equivalent shear parameters of circular honeycomb sandwich core structure based on sandwich plate theory, and uses these parameters to derive the vibration coupling control equation and the sound transmission loss under simply supported boundary condition. The correctness of the theoretical calculation is validated by finite element simulation. And, according to the theoretical calculation formula, the effects of several parameters on sound transmission of circular honeycomb structure, such as the radius and wall thickness of honeycomb core and the structural material, are analyzed. From the analysis it is discovered that the steel circular honeycomb structure with smaller core radius and thinner wall thickness has better noise isolation performance.