In order to study the influence law of different damping layer on structure vibration characteristics, based on the modal strain energy method and vibration test, the vibration characteristics of steel plates before and after laying the damping layers and constrained layers of different thickness are studied. The insertion losses and the damping loss factors of the structure before and after the radiation are compared, and it is verified that the vibration characteristics of the simulation model are in good agreement with those of the test. The results show that the larger the damping layer thickness, the lower the natural frequency and the higher the loss factor of the structure. With the increase of the damping layer thickness, the vibration damping performance of free damping plate becomes better, the vibration damping performance of constrained damping plate is not improved obviously, while with the increase of the constrained layer thickness, the vibration damping performance of constrained damping plate is improved obviously.