The effects of MgO powder addition into permeable Al2O3 refractory containing TiO2 and Al2O3 as matrixes were investigated　to　improve　the　corrosion，penetration　and　thermal　shock　resistance．Al2O3・TiO2　was　　detected　in　all　specimens．By　adding　MgO，Na2O・4MgO・15Al2O3　and　MgO・Al2O3　were　produced．The　amount　of　MgO・Al2O3　increased　as　MgO　addition　increased．The　grain　boudary　cracks　decreased　as　MgO　additon　increased．This　phenomenon　was　considered　that　the　producing　Na2O・4MgO・15Al2O3　and　MgO・Al2O3　which　were　malnly　produced　around　the　aggregate　prevented　TiO2　from　penetrating　into　the　grain　boundary．Bulk　density　increased　and　apparent　porosity　decresed　as　MgO　content　increases　and　then　showed　the　opposite　tendency　above　MgO　content　5～7wt%．Corrosion　resistance　increased　as　MgO　addition　increased　and　was　superior　by　about　two　times　compared　with　no　MgO　addition． Penetration　thickness　also　decreased　by　MgO　addition　and　showed　a　half　of　thickness　compared　with　no　MgO　addition．MgO　addition　made　strength　and　fracture　energy　increase，and　these　facts　resulted　in　the　improving　both　thermal　shock　fracture　and　thermal　shock　damage　resistance．Particulary，the　fact　that　the　penetration　thickness　decreased　by　MgO　addition　suggested　that　it　would　possible　to　operate　the　stable　bubbling　without　O2　cleaning．

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