The cushion type rolute chamber is a form of spiral case structure, because of the complex configuration of spiral case of cushion layer and it is generally difficult to control the transfer ratio of internal water pressure. For the analysis of steel spiral case in different layer elastic modulus and cushion angle under the action of self-vibration characteristics, study on the natural frequency of the self-vibration and the elastic modulus of cushion package, angular relationship. In this paper, 3D finite element model of steel spiral case was established by using a spring unit replacement cushion and the cushion and the simulation of concrete, considering the contact effects of steel and concrete, Simulation of cushion and concrete of steel spiral case role. Research shows that the natural frequency of vibration increases as the elastic modulus increases, decreases with the increase of cushion angle, the frequency can provide certain theory basis for the resonance vibration of unit.