This　study　constructs　a　comprehensive　framework　for　exploring　the　relevance　between　green　development　level　and　environmental　footprint　in　three　typical　mega　-urban　agglomerations　of　Yangtze　River　Economic　Belt　(YREB)　of　China.　This　framework　consists　of　the　three-dimensional　ecological　footprint　(EF3D),　carbon　footprint　(CF),　cloud　model,　and　Environmental　Kuznets　Curve　(EKC).　Results　reveal　that　there　exist　an　increased　EF3D　and　a　decreased　ecological　carrying　capacity　in　the　YREB,　with　annual　change　rates　of　4.45%　and　-0.46%,　respectively.　According　to　ecological　footprint　depth,　24.61,　17.59,　and　30.89　times　of　current　local　land　area　are　required　for　supporting　regional　development　in　the　YREB　upstream,　midstream,　and　downstream　urban　agglomerations,　respectively.　There　is　an　increased　tendency　in　CF,　especially　in　the　midstream　urban　agglomeration　with　an　increased　rate　of　5.25%.　Carbon　pressure　is　mostly　contributed　by　crude　oil　(34.47%)　and　raw　coal　(31.55%).　Moreover,　green　development　level　in　the　YREB　shows　an　increased　tendency　with　an　annual　rate　of　0.5%,　and　that　in　the　downstream　urban　agglomeration　is　generally　greater　than　other　areas.　The　relevance　between　green　development　level　and　environmental　footprint　is　mainly　inverted　U-shaped　or　inverted　N　-shaped　EKC　types.　CF　in　the　YREB　and　its　upstream　urban　agglomeration　begins　to　decline　when　green　development　levels　are　3.44　in　2020　and　3.26　in　2020,　respectively.　EF3D　in　the　midstream　urban　agglomeration　starts　to　fall　when　green　development　level　reaches　3.36　in　2019.　EF3D　from　cultivated　land　and　fossil　fuel　land　has　a　positive　impact　on　the　improvement　of　relevance.　Overall,　the　developed　framework　can　be　applied　to　areas　where　there　is　a　conflict　between　economic　development　and　environmental　protection.　Furthermore,　dynamic　prediction　of　green　development　level　and　environmental　footprint　as　well　as　their　correlation　mechanism　under　different　scenarios　are　still　required　for　enhancing　environmental　sustainability　and　promoting　regional　coordinated　development.