The radial temperature difference calculation of a steam drum wall is an important step in the process of calculating the low-cycle fatigue lifetime of a steam drum. So the German Standard TRD301 recommended a temperature difference computing method based on the simplified solution for the radial temperature of a steam drum wall. In order to validate the feasibility for the application of this computing method to solving the same problem of a supercharged boiler, on the basis of the reasonable simplifications to the unstable heat conduction problem across a steam drum wall, its heat-conduction equations and definite conditions were determined, then the analytical solution for the radial temperature of a steam drum wall, together with its approximate and simplified solutions, is derived. The running example of one super-charged boiler was calculated and analyzed by use of the radial temperature difference computing methods based on the approximate and simplified solutions respectively. The com-puted results show that the German Standard computing method of TRD301 has great limitations in the same problem calculation of a supercharged boiler, and it can’t apply to the researches on the same problem and its relevant problems of a supercharged boiler as a universal computing method.