Abstract: Based on the analysis of multi-stage heating 660MW unit combined with electric boiler, the method of calculating the most economical high back pressure for unit real-time operation was put forward. The experiment proved that operating under the most economical high back pressure could effectively increase the output power of the unit in controlling the main steam flow of the unit and the external heat load conditions and improve the thermal economy of unit. After the technical transformation, the heating capacity could be enhanced 440 GJ. When the external heating load was constant, multi-stage heating could decrease generator power by 86 MW and improved the peak load regulation capacity of the unit. The economy of the unit under the second gear peak shaving condition had been calculated. If the electric boiler replaced part of multi-stage heating under the same heat load, the unit conversion standard coal consumption increased by 0.32 t/h when the electric boiler load increased by 1 MW .