In　past　seismic　events,　earthquakes　have　often　caused　significant　damage　to　buildings.　It　is　noteworthy　that　most　of　the　existing　buildings　are　reinforced　concrete　structures.　Therefore,　in　order　to　mitigate　the　damage　caused　by　earthquakes,　it　is　important　to　conduct　damage　assessment　of　reinforced　concrete　structures.　Considering　that　damage　at　the　material　level　is　the　fundamental　cause　of　component　and　structural　performance　degradation,　indices　based　on　material　damage　often　have　advantages　in　reflecting　and　evaluating　component　and　structural　damage.　This　paper　proposes　a　damage　constitutive　model　for　concrete　based　on　existing　research　results.　Then,　aiming　at　the　shortcomings　of　current　research　on　steel　bar　damage　constitutive　models,　a　steel　bar　damage　constitutive　model　under　cyclic　loading　is　proposed,　reflecting　various　failure　modes　of　steel　bars　under　seismic　actions.　Based　on　this,　a　multi-level　damage　index　system　from　materials　to　components　to　structures　is　established.　Through　multi-level　experimental　simulations　and　finite　element　analysis,　the　accuracy　of　the　proposed　damage　indices　is　validated,　and　performance　indices　for　components　and　structures　are　provided.　These　indices　can　effectively　reflect　the　damaged　state　of　components　and　entire　structures　and　can　be　used　to　guide　seismic　design,　damage　assessment,　and　strengthening　design.