Flexible interaction is a key feature of smart grid. The construction of smart city puts forward new demands for the interactive operation of smart grid, but the current related researches are still relatively weak. With the methods of standardized decomposition and on-demand reconstruction, an interactive operation architecture of smart city is proposed which is analyzed from communication supports, protocol specification and security measures. Based on the architecture, the external business of smart grid is decomposed into standardized external services, the businesses of multi-source information integration service, emergency rescue and demand response are comprehensively restructured combining higher demands of smart city. Finally, a simulation model is developed on the Matlab/Simulink software, and the results show that the proposed architecture is effective.