Unified Power Flow Controller (UPFC) project in Nanjing western power system (NWPS) has been put into operation since December 2015. As the first project based on modular multi-level converter (MMC) technology in the world, it represents the highest level in the field of flexible alternative current transmission system (FACTS). Therefore, the real operation conditions of this project are important for the research and extended utilization of UPFC. In this paper, necessity and feasibility for the application of UPFC in NWPS is firstly introduced. Then, preset system-level control strategy of UPFC is discussed. Afterwards, based on load characteristics of NWPS in 2016, real system control strategy of UPFC and its balance for power flow from north and south-transferred channels is deeply analyzed. The analysis shows that the application of UPFC can effectively solve the problems of power flow misdistribution, insufficient power supply capacity and huge investment for construction of new transmission channels in NWPS. This project plays an exemplary role to promote FACTS technology for power grids with high city urbanization levels to improve power supply capability.