Abstract: To break through the inlet temperature limitation of low-temperature economizer in boiler waste heat recovery system, the tail heating surfaces of boiler were comprehensively optimized, by dividing the air preheater into two stages, and installing a low-temperature economizer between them. To make the low-temperature economizer lie in appropriate flue gas temperature range, the outlet temperature of stage II air preheater was altered, so as to obtain optimal thermodynamic working conditions. Based on technic-economic analysis, a comprehensive optimization result was finally achieved according to requirements of actual engineering practices. Results show that the standard coal consumption for power supply can be reduced by 6.7 g/(kW·h), on the basis of two-stage air preheater design and reasonable setting of key operation parameters, with the optimum thermodynamic scheme. For an average annual running time of 5 500 h, the net income may reach 21 million RMB/year according to the technic-economic analysis, indicating obvious economic benefits.