Abstract: The depth of the surface contact fatigue hardened layer of the intermediate roller of a UCM rolling mill in the normal rolling cycle was studied by means of field tracking, morphological observation, hardness detection and theoretical calculation. Suggestions for grinding operation and maintenance of the intermediate roller after normal rolling were given to reduce the risk of failure. In the normal rolling cycle, under the superposition of rolling force and cyclic contact stress between rollers, contact fatigue hardening occurred on the surface of the roller body. The hardness of the middle of the roller body increased by HSD 1~2. The hardness of the corresponding operating side has little change compared with the new roller. The hardness of the transmission side increased by HSD 5~6 at the position about 100mm away from the end under the rolling force and cyclic contact stress due to axial intrusion, and the contact fatigue hardening was obvious. According to Hertz contact fatigue theory, it was calculated that under this working condition, the maximum surface shear stress existed about 0.3 mm below the surface of the intermediate roller body (in the direction of radius). By designing the grinding amount of 0.6 mm in diameter direction, the fatigue hardening layer can be effectively removed, and the surface hardness of the roller body can be restored to that of the new roller. As a result, the risk of roller failure can be effectively reduced during the following rolling.