Abstract: Under time-varying conditions, the key points of risk decision-making are important for structural performance assessment and lifetime estimation when considering structural accumulation damage. However, the calculation of structural cumulative damage is usually involved in complex mathematical operations. Based on this, the main purpose of this paper is to propose a simplified model for estimating the structural lifetime distribution in the seismic high-incidence region. The model assumes that the cumulative damage of an existing structure is only caused by a series of earthquake actions that may occur during the design reference period. And the advantage of this method is that the structural life can be estimated by simple mathematical operation. An example application is performed on the proposed simplified structural lifetime model to verify the feasibility of the method.