The pure mass model method (PMM) which can be utilized to calculate the earthquake responses quickly for high-rise isolated structures is proposed in the paper. Firstly, transformational relations, parameters of simplified single mass model and archetype are established according to equivalent criteria for base shear and energy. And then, envelop responses of simplified model are calculated by introducing energy balance method. Energy balance method and models transformational relations are used to analyze the seismic response envelop values of every layer of archetype. The prediction formula of accelerations of high-rise isolated structure, deformation and storey shear force of superstructure and isolation layer are presented too. The suitability and calculation accuracy of pure mass model method are verified by using a 22 stories high-rise isolated structure engineering example. Results obtained from simplified calculation and numerical analysis of high-rise isolated structure show that computational results of simplified method and multi-mass model time history analysis method are comparable. The amount calculation of the method proposed is less, and parameters determination is clear and convenient with high analysis precision.