Through　the　function　transformation　of　four　disaster　loss　indexes　about　the　dead　number,　the　injured　number,　destroyed　buildings　and　direct　economic　loss　caused　by　earthquake　disasters,　the　standards　to　distinguish　these　disaster　grades　by　using　different　loss　indexes　are　unified.　In　terms　of　the　attribute　recognition　theory　and　unascertained　measurement　interval,　the　attribute　interval　recognition　evaluation　model　and　credible　identification　rules　are　established　to　analyze　indexes　and　its　reliability　degree,　thus　seismic　disaster　damage　grade　can　be　evaluated.　The　disaster　grades　of　7　important　earthquakes　in　China　from　1966　to　1983　are　divided　and　their　disaster　conditions　are　compared　by　using　the　methods.　The　results　show　that　the　method　can　evaluate　quantitatively　and　accurately　the　earthquake　damage　situation　and　the　model　has　more　advantage　than　fuzzy　method　when　disposing　unascertained　factors.