The　operation　of　a　power　system　will　inevitably　be　influenced　by　a　variety　of　natural　disasters,　e.g.　typhoon　and　forest　fire.　These　disasters　will　dramatically　change　the　operating　environment　of　a　power　system　and　increase　the　occurrence　probability　of　some　specific　faults.　It　is　important　to　make　use　of　the　disaster＇s　forecasting　information　by　combining　the　current　operating　state　of　the　network　and　some　important　components,　to　make　security　analysis　and　risk　evaluation,　so　as　to　establish　the　forewarning　mechanism,　emergency　response　mechanism,　rapid　post-disaster　restoration　and　reconstruction　mechanism　in　case　of　a　natural　disaster.　As　the　security　degree　is　measured　by　estimating　the　influence　of　contingencies　on　the　power　system,　the　predictive　contingency　set　has　a　direct　influence　on　the　security　evaluation　results　and　control　strategy.　The　contingency　selection　and　its　ranking　method　according　to　particular　natural　disaster　forecasting　information　are　discussed.　It　is　expected　to　help　achieve　on-line　security　forewarning　and　adjust　the　pre-decision　of　dispatching　according　to　the　development　of　the　specific　disaster.