Abstract: The effects of different heat treatment temperatures on the microstructure and high temperature tensile properties of TP347H furnace tube for residue hydro treating unit were studied by means of metallographic microscope,scanning electron microscope and high temperature tensile test. The results show that, with the increase of heat treatment temperature, the grain of TP347H microstructure gradually becomes coarser, the dispersed granular carbides in the microstructure do not melt, the yield strength at high temperature decreases gradually, and the tensile strength at high temperature basically remains unchanged. It is concluded that fine grain strengthening is the main factor affecting the yield strength at high temperature. When the TP347H furnace tube used in the residual oil hydrogenation unit meets the ASTM A312 standard grain size 7 grade, In order to improve the yield strength at high temperature, the grain size of grade 5-7 is the best grade.