Abstract: With the proposal of “carbon emission peak and carbon neutrality”in China,the energy industry has become the central link of transition to green and low-carbon development and the core of carbon emission reduction.As the key link connecting the preceding and the following of the integrated energy system,the urban energy system（UES） is undergoing profound changes in the production,transmission,and consumption links,which are reflected in the large-scale integration of distributed energy resource,the wide application of power electronic equipment,and the promotion and use of controllable loads,respectively.Starting from the morphological structure of the UES,this paper analyzes its multi-energy coupling functional structure with fuzzy source-load boundary and bidirectional network flow,and hierarchical spatial structure.Its typical characteristics such as openness,interconnection,mutual benefit,integrated development of energy and transportation systems,and deep cyber-physical fusion are expounded.Furthermore,two key issues,i.e.coordinated planning and optimal operation of the UES,are discussed in detail.Finally,the development path of the UES prospects from four links,including primary energy supply,secondary energy conversion,final energy consumption,and carbon removal is prospected.