There are problems of heavy workload, long time-consumption and low efficiency in field debugging of an intelligent substation monitoring system. Thus a mirror debugging method for one key sequential control system based on an expert knowledge base is proposed. A basic unit model is established based on the “Five Prevention” rules. Operational rule functions for various typical interval devices are generated, thus building a system knowledge base. A device topology connection table is constructed by parsing the system specification description (SSD) of the intelligent substation. Based on a device state-based reasoning algorithm and combined with device operational rule functions, an automatic generation of an expert knowledge base of operation tickets is implemented. A mirror debugging platform for one key sequential control system based on the expert knowledge base is built. Through intelligent electronic device (IED) mirroring simulation and the primary equipment power flow simulation and test method, a comprehensive test of the one click sequential control system is conducted. The on-site operation process is migrated to and completed in a mirror debugging platform, and a “plug and play” of image debugging results of one click sequential control system in substations is implemented. The test results indicate that the application of the platform greatly improves debugging efficiency, quality, and safety of the on-site one click sequential control system.