An iterative procedure was developed for the determination of equivalent linear stiffness and damping parameters of isolation bearings in the analysis of seismically isolated structures using CCQC (Complex Complete Quadratic Combination) response spectrum method, and a new response analysis method with iterative linearization was proposed. An example of a seven-story base-isolated frame structure was presented to demonstrate the feasibility and effectiveness of the proposed method. Numerical results of the new method were compared with those from the nonlinear transient dynamic analysis and the conventional CCQC method. It is shown that the proposed method can exclude influence of subjective factors in choosing equivalent linear stiffness and damping parameters of the isolation layer, and therefore improve the analysis accuracy and reliability.