According　to　the　emergency　response　mechanism,　it　is　necessary　to　start　the　emergency　plans　to　reduce　the　disaster　losses　when　the　emergencies　occurred.　The　start-up　mechanism　and　the　evolution　mode　of　emergency　plan　system　were　studied　based　on　the　systematic　analysis　of　disaster　consequences.　The　point,　chain　and　network　three　different　start-up　modes　of　emergency　plan　system　were　proposed　from　the　evolution　time　perspective　and　the　structural　features　of　each　mode　was　analyzed.　Finally,　the　three　start-up　modes　were　verified　through　a　real　case.　The　conclusions　conduce　to　the　reasonable　starting　of　emergency　plan　system　and　the　effectiveness　of　responding　to　emergencies.　The　conclusions　also　provide　theoretical　guidance　for　decision　of　starting　of　emergency　plan　system.