Abstract: Under the goal of "dual carbon", saving energy resources and improving utilization efficiency will be the main direction of thermal power plant research and technical innovation. As a residual heat reuse project of flue gas pipeline, low temperature economizer conforms to the basic national policy. There are social and economic benefits for long-term development of enterprises for waste heat reuse. The access mode of thermal system for flue gas residual heat utilization is modeled and simulated by ebsilon software. The accuracy of calculation results is higher than the principle of "temperature matching" of Engineering experience. Through software simulation analysis and comparison with field heat consumption test, the deviation of software simulation results and actual heat consumption values meets the engineering application requirements. The rebuilding scheme of small thermal system can be optimized by ebsilon software simulation analysis.