Risk　of　dam　break　not　only　depends　on　the　probability　of　dam　failure　events,　but　also　on　consequences.　When　the　dam　break　probability　is　known,　the　more　serious　the　dam　breaks　consequence,　the　higher　the　dam　break　risk.　The　consequence　is　the　direct　impact　of　the　dam　break,　including　health　effect　(e.g.,　death,　injury),　property　loss,　environmental　impact,　and　social　impact.　Up　to　now,　there　are　many　researches　in　the　field　of　life　loss　and　economic　loss　induced　by　the　dam　break,　but　the　researches　on　social　and　environmental　impacts　are　relatively　less.　The　index　system　is　presented　for　the　evaluation　of　the　social　and　environmental　effect　of　dam　break,　based　on　the　analysis　of　the　influence　of　the　dam　break　on　the　society　and　environment.　Multi-target　methods　and　stage　division　are　also　proposed.　The　analytic　hierarchy　process　is　used　to　elicit　the　weight　of　each　target.　The　fuzzy　mathematics　method　is　used　to　assess　the　degree　of　dam　break　impacts　on　the　society　and　environment　with　the　principle　of　maximum　degree　of　membership.