To　enhance　the　anti-flood　capacity　of　mountain　highway,　the　flood　damage　of　highway　drainage　facilities　at　mountain　is　investigated,　the　damage　mechanism　is　analyzed,　the　compositions　of　the　drainage　system,　named　slope　rain　boundless　unit,　drainage　canals　unit　and　little　bridge-culvert　unit,　are　studied.　The　evaluating　indices　system　about　the　anti-flood　ability　of　the　drainage　system　is　developed.　The　indices　include　the　evaluation　of　environmental　disaster,　the　evaluation　of　the　damage　of　drainage　systems,　the　evaluation　of　economic　losses,　the　evaluation　of　the　benefits　of　anti-flood　facilities.　The　relevant　economic　calculation　and　the　evaluation　standards　are　put　forward.　The　application　results　show　that　this　indices　system　has　an　obvious　guiding　role　for　the　decision-making　in　mountain　highway＇s　anti-flood.