The　adsorption　behavior　of　radioiodine　(I-2)　molecules　on　three　different　low-index　surfaces　of　cuprous　oxide　(Cu2O)　was　systematically　investigated　using　first-principles　density　functional　calculations　with　periodic　slab　models.　The　role　of　typical　surface　adsorption　sites　was　evaluated　by　calculating　structural　parameters　of　the　adsorption　configurations　and　energy　features.　Moderate　geometry　relaxation　of　the　three　low-index　surfaces　was　observed.　The　results　of　geometry　optimization　and　total　energy　calculations　indicated　that　the　Cu2O(100)　and　(111)　surfaces　exhibit　higher　reactivity　towards　I-2　adsorption　than　the　Cu2O(110)　surface.　The　surface　oxygen　site　(O-s)　was　determined　to　be　the　most　favorable　adsorption　site　on　the　Cu2O(100)　surface,　while　the　coordinatively　unsaturated　copper　site　(Cu-cus)　was　energetically　preferred　on　the　Cu2O(111)　surface.　In　addition,　the　electronic　structure　information　for　several　typical　configurations　were　explored　to　explain　the　detailed　interaction　mechanism　of　adsorbed　systems.