Abstract: The fracture reason of a armored thermocouple cable with GH3128 superalloy protection tube was analyzed, and the process improvement measures were proposed. The results show that there were pits in the inner wall of the protection pipe, and magnesium oxide was embedded, so that the inner wall was subjected to greater stress during the drawing process, which increased the probability of crack initiation. The inner and outer walls of the protective tube of armored cable were subjected to large stress, which caused the material to segregate, and the microstructure of the material was extremely uneven, and finally led to the fracture of armored cable in the bending process.