Due　to　high　degreenetworking　of　the　secondary　system　of　smart　substation,　the　information　exchange　relationship　of　secondary　equipment　is　hidden　and　invisible,　causing　inconvenience　in　the　work　of　maintenance　safety　measures.　This　paper　explores　the　application　of　graph　theory　in　secondary　system　safety　measures　of　intelligent　substation.　Firstly,　in　order　to　obtain　the　virtual　circuit　configuration　of　the　secondary　system,　this　paper　uses　document　object　model　(DOM)　to　read　and　analyze　substation　configuration　description　(SCD)　file.　Secondly,　a　network　topology　model　expressing　the　information　interaction　relationship　of　intelligent　electronic　devices　(IEDs)　is　established　using　graph　theory　knowledge,　and　a　status　matrix　of　IEDs　is　established　by　distinguishing　the　maintenance　status　of　IEDs　according　to　maintenance　task.　Finally,　combined　with　link　security　measure　rules,　an　assistant　analysis　model　of　security　measure　policy　is　established,　and　the　implementation　suggestions　of　security　measures　are　given.　This　paper　takes　the　first　inspection　of　a　500kV　circuit　breaker　in　Donggang　substation　as　an　example,　and　effectiveness　and　correctness　of　the　method　in　secondary　maintenance　safety　measures　are　verified.　©　2020,　Power　System　Technology　Press.　All　right　reserved.