Abstract: To reduce power consumption rate of coal-fired units during deep peak shaving operation, a mechanism model suitable for low-load conditions was established based on a 660 MW unit as the research object. The reliability of the model was verified using actual operation data. Based on thermodynamic theory, the energy consumption distribution characteristics of the unit under low-load conditions were analyzed, and the strategy was proposed to improve the relative internal efficiency of the steam turbine under low-load conditions by adjusting the working fluid flow rate. Results show that compared with the rated condition, the theoretical cycle efficiency decreases by 4.67% under the low-load condition, the boiler efficiency decreases by 0.43%, and the relative internal efficiency of the steam turbine decreases by 8.96%. After comparing before and after flow adjustment, it is found that the unit operates with simultaneous temperature and pressure changes under low-load conditions, which has higher thermal economy than the original sliding pressure operation. Taking 198 MW as an example, after adjusting the flow rate, the relative internal efficiency of the steam turbine increases by 1.57%, and the power consumption rate decreases by 1.137 g/(kW·h). Under the operating conditions of 130, 230 and 340 MW for the unit, after adjusting the flow rate, the power consumption rates are reduced by 1.147, 0.067 and 0.313 g/(kW·h), respectively. The study can provide certain reference for optimizing the flow rate operation of coal-fired units during deep peak shaving conditions.