Abstract: Based on the influence of specifications of finned tube and parameters of steam on the heat transfer characteristics, weight of steam air preheater, and the operation benefit of waste-incinerated boiler, a comprehensive evaluation method on the basis of technique for order preference by similarity to an ideal solution（TOPSIS） was proposed. Firstly, the evaluation index system was constructed with the weight of finned tube, air resistance, heat-exchange area, weighted average heat transfer coefficient, saturated steam volume, turbine steam extraction volume, boiler output, effective heat output of boiler and thermal efficiency, and the index weight was determined by information entropy. Secondly, the approach degree between each scheme and positive and negative ideal solution was calculated by the improved relative approach degree method. Furthermore, the preference order of complete ordering of 20 design schemes was generated. Finally, the validity of TOPSIS method was verified by testing and analyzing, and the design scheme of steam air preheater was optimized.