Abstract: Based on the historical operation data of the unit,by constructing an analysis model of the regenerative system,the operation parameters of the regenerative system are compared and analyzed under the same load condition,and the problem of low feedwater temperature of the unit is analyzed by means of remote diagnosis.The results show that the low feedwater temperature of the unit is mainly caused by the decline of heat exchange performance of the heater and the poor matching between extraction parameters and heater performance.The disintegration of high-pressure heater verified the accuracy of remote diagnosis.Through the optimization of operation parameters and the improvement of heater maintenance,the feed water temperature of the unit increased by 2.8℃,which improved the operation economy of the unit.Relying on big data,remote diagnosis of unit faults can effectively alleviate the problem of low feedwater temperature of the unit.