In　this　work,　the　uniform　Cu2O　submicron-cubes　were　facilely　synthesized　by　liquid　phase　reduction　method.　Then,　the　Cu2O　submicron-cubes　were　further　oxidized　into　Cu2O-CuO　heterojunction　with　tunable　Cu2+/Cu+　ratios　and　CuO　submicron-cubes　by　controlling　the　calcination　temperature.　The　phase　transition　period　during　calcination　was　real-time　monitored　by　the　in　situ　XRD　and　in　situ　DRIFTS.　The　obtained　materials　were　investigated　as　the　catalysts　of　CO　oxidation.　The　results　revealed　that　the　Cu2O-CuO　heterojunction　catalysts　performed　much　higher　catalytic　activities　than　the　Cu2O　and　CuO　counterparts.　Because　the　synergistic　effect　of　the　heterojunction　(Cu2+/Cu+)　could　increase　the　surface　oxygen　vacancy　concentration.　Furthermore,　it　was　also　found　that　only　the　Cu2O-CuO　heterojunction　structure　with　the　appropriate　Cu2+/Cu+　ratio　behaved　the　optimum　catalytic　activity.　The　kinetic　studies　indicated　that　the　apparent　activation　energy　of　CO　oxidation　was　greatly　affected　by　the　Cu2+/Cu+　ratio.　Therefore,　these　Cu2O-CuO　submicron-cubes　with　heterostructure　were　considered　as　the　promising　CO　oxidation　catalysts.　(C)　2021　The　Korean　Society　of　Industrial　and　Engineering　Chemistry.　Published　by　Elsevier　B.V.　All　rights　reserved.