Abstract: To put the SCR system into safety operation at low load of a utility boiler, a retrofit scheme was proposed by adopting the economizer system with feedwater redistribution, where a part of low-temperature feedwater is bypassed directly to the downcomer, and a part of hot water is recirculated from the economizer outlet to the inlet. Results show that the economizer system with feedwater redistribution can help to improve the inlet tempemperature of working medium in the economizer, reduce the heat-transfer temperature difference, reduce the quantity of heat transfer, and improve the flue gas temperature at economizer outlet, i.e. improve the flue gas temperature at SCR inlet, thus achieving safety operation of the SCR facility during low load operation of the boiler. After retrofit, the boiler is now able to operate safely and stably, and the NO_x emission is reduced accordingly due to the SCR unit coming into use.