In order to improve boiler efficiency and reduce the emission of boiler pollutants, this paper take a power plant as the research object, the overall optimization of the boiler's air preheater seal device horizontal flue ash blower system and high-pressure economizer.were carried out, chemical cleaning and heat treatment were also carried out for bolier, and the thermal efficiency and pollutant discharge of the boiler ware tested before and after the optimization. Compared with that before the optimization, the efficiency of boiler is increased by 2.3% under different loads and the coal consumption is reduced at the same time. The unburned carbon heat loss and the air leakage rate of air preheater is also greatly reduced. The concentration of NOx discharged from the boiler has reached the requirement. The optimized reform has achieved the expected effect.