One　important　mission　of　the　newly　launched　Landsat-9　is　to　collaborate　with　Landsat-8　to　reduce　the　revisit　period　of　Landsat　Earth　observations　to　eight　days.　This　requires　a　high　level　of　consistency　between　the　two　satellite　data.　Previous　cross-calibrations　between　Landsat-8　Operational　Land　Imager　(OLI)　and　Landsat-9　OLI2　have　been　performed　via　band-by-band　approaches,　and　the　spectral　deviation　revealed　between　the　two　sensors　was　within　1%.　However,　it　remains　uncertain　whether　this　deviation　will　persist　when　multiple　bands　are　combined　to　perform　certain　calculations　and　whether　the　offset　found　in　each　band　will　be　amplified　in　the　combined　multiband　performance.　Therefore,　a　comprehensive　cross-comparison　using　a　multiband　combination　approach　is　necessary　to　ensure　agreement　between　the　two　sensor　data.　This　study　conducted　a　multiband　combination-based　cross-comparison　using　simultaneous　underfly　data　of　both　sensors　along　with　a　Tasseled　Cap　Transform　(TCT)　performance.　The　coefficients　of　Landsat-8　were　utilized　to　calculate　the　three　components　of　Landsat-9　TCT.　The　calculation　of　the　TCT　involves　six　bands　of　both　OLI　sensors,　which　enables　a　more　thorough　examination　of　the　consistency　of　the　two　sensor　data.　In　addition,　calculating　Landsat-9　TCT　directly　using　Landsat-8　coefficients　allows　further　investigation　of　the　similarity　between　the　two　sensors　by　determining　whether　Landsat-8　TCT　coefficients　are　suitable　for　Landsat-9　TCT.　Both　top　of　atmosphere　(TOA)　reflectance　data　and　surface　reflectance　(SR)　data　were　employed　for　this　comparison.　Apart　from　whole　image　pair-based　comparisons,　land　cover　category-based　comparisons　were　also　performed.　The　results　show　that　the　three　TCT　components　of　Landsat-9,　calculated　using　Landsat-8　coefficients,　are　similar　to　those　of　Landsat-8,　with　an　average　R2　of　0.983　and　RMSEs　on　the　order　of　0.009　in　most　scenarios.　The　deviations　observed　in　the　TCT　components　between　the　two　sensors　are　primarily　due　to　the　higher　radiometric　resolution　of　Landsat-9　(14　bits)　compared　to　Landsat-8　(12　bits),　as　the　deviations　occurring　in　bright　and　dark　areas　are　larger　than　those　in　other　areas.　Besides,　the　uncertainty　in　the　green　band　for　vegetative　targets　and　the　uncertainty　revealed　in　typical　vegetative　surfaces　also　contributed　to　the　higher　divergence　in　the　greenness　component.　The　1%　difference　detected　in　band-by-band　cross-calibrations　increased　by　0.2-0.5　percentage　points　in　this　comprehensive　multiband　comparison.　Overall,　this　cross-comparison　study　generates　confidence　that　the　Landsat-8　OLI　and　Landsat-9　OLI2　data　are　in　strong　agreement　even　when　performing　multiband　combination　operations.　This　demonstrates　that　the　synergistic　use　of　the　two　sensor　data　can　well　maintain　the　continuity　of　Landsat　Earth　observations.