Mine　ventilation　system　which　was　the　important　constituent　of　coal　mining　system　ensured　the　safety　production　as　critical　measures.　Construction　and　quantification　of　evaluation　index　system　for　mine　ventilation　system　was　the　basis　and　standard　of　comprehensive　evaluation　of　system＇s　defect.　This　paper　began　with　hazard　factors　which　caused　ventilation　accident,　investigated　the　direct　and　indirect　reasons,　and　then　carried　on　a　qualitative　analysis　of　Fault　Tree.　According　to　analysis　results,　an　evaluation　index　system　of　ventilation　system　was　constructed　and　the　index　was　also　quantified　by　use　of　AHP.　Since　that　existing　index　system　was　improved　and　supplemented,　it　is　supposed　to　improve　the　operational　capability　and　rationality　of　daily　management　as　well　as　safety　evaluation　of　mine　ventilation　system.