To　solve　the　problem　of　post　disaster　assessment　of　bridges　after　accidental　explosion,　terrorist　attack　and　weapon　strike　during　service,　the　damage　and　damage　evaluation　of　a　real　single　box　three　chamber　reinforced　concrete　box　girder　structure　under　explosion　load　were　carried　out　by　using　ANSYS/LS-DYNA　finite　element　software,　and　its　damage　and　failure　modes　under　different　explosion　positions　and　explosive　equivalent　were　analyzed.　It　is　found　that　under　100　kg　and　200　kg　explosive　equivalent,　the　reinforced　concrete　box　girder　was　mainly　damaged　locally,　the　damage　of　a　single　box　chamber　was　large,　and　the　overall　damage　of　the　box　girder　was　limited.　The　explosion　above　the　box　girder　web　and　inside　the　box　chamber　caused　serious　damage　to　the　box　girder.　The　damage　evaluation　method　of　box　girder　based　on　the　section　residual　moment　of　inertia　was　proposed.　It　is　suggested　that　the　damage　and　failure　of　box　girder　structure　under　explosion　load　can　be　divided　into　four　levels:　mild　damage,　moderate　damage,　severe　damage　and　complete　damage.　The　damage　and　failure　of　box　girder　structure　under　explosion　load　were　evaluated.　©　2022,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.