Abstract: In this paper,the failure reason of the pipes transporting boiler′s surplus heat are analyzed. After a comprehensive study on chemical composition,microsturcture,fractures and cracks,the results show that the fractures occured under the effects of combined freting and erosion of the airflow from the flue,it is suggested to use steel with high temperature strength and high anti-erosion,at the same time,strictly controlling the content of sulfur and oxygen in the flue is necessary.