Based on the data of induced draft fan performance test,three retrofitting projects of the induced draft fan are introduced,and retrofitting design parameters are determined carefully.Technical features of three retrofitting projects are contrasted and analyzed.Finally,the right induced draft fan is retrofitted into Y4-60-14№25F.After retrofit,the efficiency of the induced draft fan is raised by about twelve per cent,energy saving rate is up to about twenty per cent,economic benefit is prominent.