Purpose　-　By　studying　the　green　development　efficiency　(GDE)　of　33　cities　in　the　provinces　of　Jiangsu,　Zhejiang,　and　Fujian　in　China,　this　study　strives　to　conduct　an　analysis　of　the　sustainable　practices　implemented　in　these　developed　regions,　and　derive　valuable　insights　that　can　foster　the　promotion　of　green　transformation.　Design/methodology/approach　-　First,　the　urban　green　development　system　(GDS)　was　decomposed　into　the　economic　benefit　subsystem　(EBS),　social　benefit　subsystem　(SBS),　and　pollution　control　subsystem　(PCS).　Then,　a　mixed　network　SBM　model　was　proposed　to　evaluate　the　GDE　during　20152020,　with　Moran＇s　I　and　Bootstrap　truncated　regression　model　subsequently　applied　to　measure　the　spatial　characteristics　and　driving　factors　of　efficiency.　Findings　-　Subsystem　efficiency　presents　a　distribution　trend　of　PCS　＞　EBS　＞　SBS.　There　is　a　particular　spatial　aggregation　effect　in　EBS　efficiency,　whereas　SBS　and　PCS　efficiencies　have　no　significant　spatial　autocorrelation.　Furthermore,　urbanization　level　contributes　significantly　to　the　efficiency　of　all　subsystems;　industrial　structure,　energy　consumption,　and　technological　innovation　play　a　crucial　role　in　EBS　and　SBS;　external　openness　is　a　pivotal　factor　in　SBS;　and　environmental　regulation　has　a　significant　effect　on　PCS.　Originality/value　-　This　study　further　decomposes　the　black　box　of　GDS　into　subsystems　including　the　economy,　society,　and　environment.　Additionally,　by　employing　a　mixed　network　SBM　model　and　Bootstrap　truncated　regression　model　to　investigate　efficiency　and　its　driving　factors　from　the　subsystem　perspective,　it　endeavors　to　derive　more　detailed　research　conclusions　and　policy　implications.