Abstract: A coupling method of direct and inverse heat conduction problems was proposed for transient temperature calculation of a pressurized boiler drum, of which the locally heated outer surface is divided into two regions, namely heated and unheated area. For the unheated area, the inverse method is used to determine the temperature field by circumferentially arranging thermocouples to measure the outside surface temperature of the drum, and for the heated area, the direct method is adopted to solve the temperature field; whereas at the junction of above two areas, the temperatures determined by the inverse method are used as known boundary conditions to calculate the temperature field of heated area by the direct method. By this way the coupling solution of direct and inverse heat conduction problems is realized, and the whole temperature distribution of the drum is obtained. A comparison was made to the drum temperature distribution during cold startup of the boiler respectively obtained by Ansys software and the coupling method. Results show that the coupling method of direct and inversion heat conduction problems has high precision and strong adaptability under complicated boundary conditions, which therefore may be used in actual engineering projects.