Abstract: The TP347H austenitic stainless steel heating surface tube of the rear platen reheater of a power plant cracked. The cracking cause was analyzed by macroscopic observation, scanning electron microscopy and energy spectrum analysis, room temperature tensile test and other methods.The results show that the TP347H austenitic stainless steel heating surface tube had brittle cracking, and its microstructure aging level was 4.5. After the heating surface tube was overheated for a long time, coarse carbides were precipitated at the grain boundary, the microstructure deteriorated, and the brittleness of the material increased, resulting in cracking of the tube.