Discrete　Element　Method　(DEM)　can　well　simulate　the　failure　of　geomaterials,　but　it　is　challenging　to　evaluate　its　stable　degree　and　failure　state.　An　approach　for　calculating　the　equivalent　Cauchy　stress　field　in　both　regular　and　irregular　DEM　models　is　proposed　by　establishing　a　local　equivalent　element　for　each　particle.　Meanwhile,　the　relationship　between　the　stress　ratio　path　during　geomaterial　failure　and　the　macro　strength　criterion　is　analyzed,　and　then,　a　new　evaluation　index　named　SFSRP　is　proposed.　Combining　the　equivalent　Cauchy　stress　and　the　SFSRP,　a　method　that　can　evaluate　the　stable　degree　and　failure　state　of　the　geomaterial　is　established.　Finally,　the　proposed　method　is　implemented　to　analyze　the　failure　process　in　four　typical　cases,　including　a　trapdoor　test,　a　retaining　wall　test,　a　tunnel　excavation　test,　and　a　biaxial　compression　test,　based　on　PFC2D.　The　results　demonstrate　that　the　proposed　method　not　only　presents　the　failure　location　intuitively　but　also　quantitatively　reflects　the　stable　degree　and　failure　state　in　the　DEM　model.