The status and role of smart grid in smart city construction has not been fully excavated. Based on the systematic combing smart city architectures, the mutual promotion and restriction effects between smart grid and smart city are analyzed, and some quantitative analysis is made for the coordination and supporting effects. Finally, the key technologies and applications of smart grid to support the construction of smart city are systematically researched. It is pointed out that energy technology is the basic support technology of smart city as information communication technology (ICT), smart grid and smart city have a relationship of mutual promotion or restriction within the scope of their intersection, a hierarchical distribution characteristic is shown for the technologies and applications of smart grid according to their effects of supporting to smart city construction.