Abstract: Nonproportional viscous damping is used to simulate the effect of frictional constraint at the shroud interfaces.The effects on the natural vibration behavior and dynamic response are investigated.The damping matrix and stiffness matrix of the interfaces in local coordinate system are presented by using the equivalent viscous damping and stiffness coefficients of the spring/friction model.The response displacements and the corresponding response stress distributions of the coupling system under three kinds of boundary conditions at shroud contact interfaces are obtained respectively by using mode superposition method.The calculation method,the basic analysis approach and the important conclusions provided in the paper may be available for reference in the designing,development and modification of turbomachinery.