Abstract: According to the issue of low flue gas temperature at the air preheater inlet of a power plant boiler, the increase in exhaust gas temperature is due to poor heat exchange efficiency of the air preheater, the issue affecting the output of the boiler.The high temperature heat exchanger element in the air preheater is replaced and the high temperature heat exchanger element is increased by 300 mm.At the same time, the swing angle of the burner is adjusted during the inspection, which meets the requirements of the full output of the boiler and reduces the exhaust gas temperature.It is feasible to analyze the transformation effect, the return on investment and the safety and economic plan after the transformation, which provides reference for the transformation of equivalent units.