Microtopography　is　an　important　and　complicated　factor　of　affecting　lightning　strike　trip-out.　The　rule　of　how　microtopography　affects　lightning　strike　to　the　transmission　line　is　explored　based　on　geographic　information　systems(GIS)　and　Excel.　How　to　form　the　files　of　transmission　line　and　lightning　strike　information　by　using　GIS　is　introduced.　Combined　with　the　microtopography　of　GIS,　lightning　strike　data　collected　from　the　electric　power　company　are　analyzed.　The　correlation　rules　between　exposed　surface　and　fault　phases　of　110,　220　and　500　kV　transmission　lines　caused　by　lightning　strike　are　obtained.　And　some　characteristics　of　lightning　selectivity　affected　by　microtopography　factors　including　peak,　river,　valley,　mountain　ridge,　windward　slope　and　so　on　are　explored.　The　results　show　that　this　statistic　analysis　method　is　very　intuitive　and　imaginal.　And　the　results　can　provide　references　for　the　path　design　of　transmission　line　and　the　selection　of　lightning　protection　measures.