Abstract: The quantitative assessment for the seismic resilience of engineering systems is the cornerstone of building "Resilient Urban and Rural". However, there is still a lack of a universal model that can accurately simulate the post-earthquake functional recovery of the system and a probabilistic quantitative assessment method for the seismic resilience that can fully consider the influence of associated uncertainty factors. Taking one substation engineering system as an example, the post-earthquake functional recovery simulation method based on the supply and demand relationship of repair resources was introduced. Combined with the system seismic vulnerability analysis based on Monte Carlo simulation, the method flowchart for evaluating the system's seismic resilience was developed. By further integrated with the seismic hazard risk, a probabilistic quantitative method for assessing the seismic resilience of a system was put forward using risk curves and risk surfaces. The effectiveness of the method proposed was verified by simulating the post-earthquake functional recovery, by identifying key uncertainty factors, and by assessing seismic resilience risk for a real-world substation system. It provides a new and beneficial tool for seismic resilience assessment, resilience target determination, and resilience improvement measures investigations for engineering systems in a probabilistic manner.