The　trilemma　of　economic　growth,　energy　sustainability　and　environmental　protection　is　facing　China＇s　urban　sustainable　development　In　this　paper,　the　ecological　network　analysis　is　applied　to　evaluate　the　whole　metabolic　processes　of　urban　energy　system.　Then,　a　hierarchy　analysis　is　conducted　to　diagnose　and　describe　the　energy＇s　impacts　on　the　whole　energy　metabolic　processes,　and　reflect　the　dynamics　and　evolution　of　urban　energy　metabolic　system.　Using　Beijing　as　a　case　study,　results　suggest　that　Beijing＇s　strongest　energy　metabolic　flows　are　electricity　-＞　service　and　electricity　-＞　industrial　energy　use.　Meanwhile,　the　main　inflow　to　electricity　has　switched　from　raw　coal　in　2008　to　natural　gas　in　2016.　The　hierarchy　analysis　indicates　that　the　impacts　of　Natural　gas　and　other　energy　are　increasing　while　that　of　raw　coal　is　decreasing.　These　results　also　suggest　that　Beijing＇s　current　achievements　on　urban　energy　system　optimization　mainly　rely　on　structural　variation　in　industries.　It　is　considered　that　the　future　optimization　should　concentrate　on　promoting　clean　energy　utilization　in　Beijing.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.