Abstract: The discussion involves the heat treatment process for the large-sized heavy-walled boiler tube in 12Cr1MoV. Relevant experiment result shows that the structure and properties of the said boiler tube can not be ensured unless proper cooling step is added to the heat treatment process, which ensures the steel structure with 30%~40% tempering bainite and 60%~70% ferrite or pearlite, thus good overall performance of the tube.