In order to achieve lowfrequency broadband vibration reduction, the star honeycomb and the concave hexagonal honeycomb are combined to form a composite negative Poisson's ratio honeycomb structure. The dispersion curve of the composite honeycomb cell is obtained by COMSOL Multiphysics software with Floquet periodic boundary conditions. The transmission characteristics of the finite periodic structure are calculated to verify the existence of the band gap in the dispersion curve. The composite honeycomb superstructure plate sample is designed and prepared. The response of the composite honeycomb plate under elastic wave excitation is analyzed by experiments to verify the finite element analysis results. Genetic algorithm is used to optimize the structure parameters, and several wide bandgaps are opened at 1000~2000Hz, which provides useful guidance for bandgap design. Finally, the vibration spectrum of the floor obtained from the real subway test is used as excitation to simulate the vibration reduction performance of the superstructure. The results show that the composite honeycomb superstructure plate can effectively attenuate the vibration peak of the train floor in 1000~2000Hz.