CO2 emission monitoring and calculating of power system is fundamental for low-carbon development of electric power industry. Current calculating and analysis methods for CO2 emission from power system are mostly theoretical. The application of CO2 emission monitoring and analysis in existing projects is scarce. In Gongqing city of Jiangxi province, a comprehensive low-carbon benefit simulation and evaluation system is established in the smart grid demonstration project. In this paper, application of low-carbon benefit simulation and evaluation system is introduced based on this demonstration project. On the basis of overview of demonstration project and overall framework of low-carbon benefit simulation and evaluation system, specific functions are introduced in terms of CO2 emission on-line monitoring, low-carbon planning simulation and comparison, and low-carbon planning benefit analysis. Moreover, benefits derived from demonstration project under different cases are shown, which are calculated by that system. Finally, prospects of application value of low-carbon benefit simulation and evaluation system are discussed.