At present, the analysis of structure safety status of concrete dams using the monitoring data under strong earthquake is greatly influenced by calculation models and parameters. Based on the time series of the monitoring data under strong earthquake, the time-varying autoregressive recursive ARX model is established. The post-earthquake rapid evaluation method of concrete dams is then proposed based on the property that the ARX model parameters can reflect the dynamic variation of the structure system, and the efficiency of the model is improved by using the self-regulated forgetting factor. The simulation results for an example show that the time-varying parameters of ARX model can reflect the structure state variation of concrete dams, indicating that the proposed method is effective and feasibility and it can be a supplementary method to the Technical Specification of Strong Motion Monitoring for Seismic Safety of Hydraulic Structures(DL/T 5416-2009).