Abstract: In view of the current situation of backpressure extraction steam turbine (BEST) regenerative system design for advanced ultra-supercritical coal-fired units, the influence of BEST on energy consumption of 700℃ coal-fired units with single and double reheat system was compared and analyzed. Based on parameter matching and system optimization method of steam turbine flow and regenerative system, the idea of optimizing regenerative system from the system perspective was put forward. The results show that the coal consumption of 700℃ double reheat coal-fired units with BEST is lower than that of single reheat units, and the coal saving advantage is more obvious at low load. The coal saving is 11.7g/(kW·h) at 40% load. 700℃ double reheat units with BEST is more economical for peak adjustment than single reheat units, and 700℃ single reheat units with BEST is more suitable for high load operation units. With the reduction of load, the extraction superheat of 700℃ double reheat units with BEST increases continuously, therefore, the extraction position of BEST can be adjusted backward to match the minimum coal consumption. In addition, a method of matching the extraction parameters of the regenerative system with the flow parameters of the steam turbine was proposed to optimize the whole system of the units. Based on this method, the BEST can be cancelled, but the load distribution and flow design of the three cylinders of the steam turbine need to be redesigned.