Aiming at the problem of how to effectively and reliably isolate the relevant secondary equipment during the expansion, rebuilding and overhaul of the smart substation, this paper presents a method of security measures online rehearsal and antierror warning of intelligent substation secondary equipment. This method establishes substation graphics files through the SCD model file, and correlates the information collected by the data acquisition unit and the substation graphics file, to get the initial state of substation safety measures while conducting rehearsal of secondary equipment safety measures and dynamically previewing the safety process rehearsal process. The example validation shows that the method can automatically warn against the incomplete safety isolation and provide an effective technical means for the maintenance personnel in the intelligent substation.