Abstract: Based on research of Kelly,et al,a multiple-degree-of-freedom structure was simplified to its equivalent two-degree-of-freedom model structure according to equivalent criteria for equal structure period,total base shear and total base moment.After numerical analysis of some regular-shock-insulation building structures,simplified computing formula for system parameters of the model structure has been obtained.Thusly,maximal earthquake response of a structure can be solved by applying response-spectrum-analysis method to its corresponding equivalent simplified model structure.The equivalent simplified model structure is simple,and even computer will not be needed when the model structure is utilized.Once the equivalent method is applied to a highrise shock-insulation structure,maximal earthquake response of the structure will be accurately forecasted.Advantages of the method have been verified by some computational examples.It implies that a practical design method is provided for the highrise shock-insulation structure.