Abstract: The design and selection margin of forced draft fan is too large,the opening of the inlet guide blade is small during operation,the operating efficiency point deviates from the performance efficiency area,and the regulation performance is poor under low load. In order to improve the regulating performance and operating efficiency of forced draft fan,the feasibility study of technical transformation of forced draft fan is carried out in combination with the actual conditions. The two technical routes of variable frequency speed regulation and permanent magnet speed regulation are comprehensively compared and analyzed,and the transformation scheme of permanent magnet speed regulation is finally selected.