Firstly, the ANSYS finite element software was applied to study thermal analysis of the fin-tube with trigonal sections in order to acquire the temperature contours, which showed that at the round of pipe the temperature reached the maximum value from the image. The varied temperature tendency of vertical direction with the fin and axial direction of the pipe were analyzed to get respectively the temperature curve and the temperature contours by definition of the path. What was more, the indirect method was applied for thermal stress analysis at the basis of thermal field in order to require distribution situation of thermal stress by corresponding path. It turned out that thermal stress mainly focused on pipe and the joints of the pipe and fin. At last, according to the analytical and design standard for steel pressured vessels, the assessment of the corresponding stress was analyzed to prove its security in the simulative environment, making the basis of reference for further research.