Al-doped　Co3O4　and　CoO　are　prepared　from　Co-Al　hydrotalcite　by　calcination　in　air　and　N-2　atmospheres,　and　characterized　by　TG-DTA,　XRD,　SEM,　N-2　adsorption,　Raman,　XPS,　and　H-2-TPR.　Co-Al　hydrotalcite　is　oxidized　to　Co(Co,Al)(2)O-4　in　air　accompanying　with　the　collapse　of　layered　structure,　while　in　N-2　it　decomposes　to　Co(Al)O　that　remains　the　plate　morphology　of　hydrotalcite.　In　both　cases,　Al3+　is　doped　into　the　lattice　of　cobalt　oxides,　leading　to　marked　changes　in　the　crystal　size,　surface　state,　and　reducibility.　Especially,　Al-doped　CoO　shows　smaller　crystal　size　(4.1　nm),　larger　surface　area　(172　m(2)　g(-1)),　and　higher　degree　of　structural　disorder　than　Al　doped　Co3O4.　Meanwhile,　the　Al-doped　cobalt　oxides　show　different　reducibilities　to　those　of　Co3O4　and　CoO,　indicating　a　strong　interaction　between　cobalt　and　aluminum.　The　N-2-calcined　sample　exhibits　higher　activity　for　benzene　combustion　than　the　air-calcined　sample　as　well　as　a　relatively　good　stability　during　heating/cooling　cycles　and　a　good　long-time　durability.　Under　the　reaction　atmosphere,　Co(Al)O　is　transferred　to　Co(Co,Al)(2)O-4.　The　resulting　Co(Co,Al)(2)O-4　remains　the　original　plate　morphology　and　textural　property　and　presents　abundant　surface　adsorbed　oxygen　species,　which　accounts　for　its　high　activity.