The　coordination　of　economy,　energy,　and　environment　plays　an　important　role　for　cities　seeking　green　transformation　and　sustainable　development.　However,　poor　information　and　equivocal　data　are　what　often　face　the　related　analysis.　In　this　paper,　the　correlation　and　synergy　of　the　urban　economy-energy-environment　system　are　analyzed.　First,　the　Grey　relational　analysis　and　entropy　weight　method　are　combined　and　introduced　to　analyze　the　correlation　degree　in　the　indicator　level　and　the　subsystem　level　of　the　3E　system.　Then,　the　concepts　of　ordinal　parameter　and　comprehensive　correlation　degree　are　introduced,　to　evaluate　the　ordering　degree　of　subsystems　and　the　synergy　degree　of　compound　systems.　Finally,　the　data　of　Beijing　from　2008　to　2017　are　used　for　empirical　study.　Results　suggest　that　a　fluctuating　tendency　of　low　synergy　or　none　synergy　is　observed　in　the　Beijing　3E　system.　Furthermore,　the　improvement　of　the　energy　subsystem　displays　dominant　effects　on　the　coordinated　development　of　compound　systems,　and　the　technological　innovation　and　structural　optimization　in　industries　could　help　to　improve　the　Beijing　economy-energy-environment　system.