Abstract: During the production and commissioning process of a certain hot rolling mill, the rolling mill suddenly stopped and the high chromium iron rolling mill broke. The causes of rolling mill fracture were analyzed using macroscopic observation, chemical composition analysis, mechanical property testing, metallographic examination, scanning electron microscopy and energy spectrum analysis, X-ray diffraction analysis. The results show that the fracture mode of the rolling mill was fatigue fracture, and there were obvious network turtle cracks and large block like and flake like peeling in the crack source area on the surface of the rolling mill. The sudden emergency stop and shutdown of the cooling water of the rolling mill caused a huge temperature difference between the surface and the core of the rolling mill, formed a large thermal stress. The cracking and peeling areas on the surface of the rolling mill produced stress concentration, promoted the continuous expansion of cracks and ultimately led to the fracture of the rolling mill.