Air distribution fan for sulfur recovery unit in natural gas treatment plant is drived by constant speed motor and operates under power frequency. When process load drops, extra air will be vented so as to ensure stable operation of equipment. In order to reduce air vent and save energy as much as possible, in combination with the characteristics of centrifugal fan, conducted is analysis on energy-saving operation and optimization control scheme of sulfur recovery unit fan based on actual surge characteristic test data on different frequency of sulfur recovery unit fan in certain natural gas purification plant and results show that adoption of frequency conversion and speed control scheme can adapt to process changes and obtain good energy-saving effect.