Aiming at the abnormal sound and bearing failure of the extra large four row tapered roller bearing used in piercing mill of a steel factory in China, the appearance, microstructure, size and hardness of the failure bearing are checked. The bearing material and surface hardness were judged to be up to the standard. The analysis was shown that the crack was caused by the severe friction and heat of the big edge and the roller end surface. Dimensional deformation was caused by improper heating and cooling measures during installation and removal. Since the tilt of the middle and outer ring of the installation results in uneven clearance of the bearing columns, the B column being more stressed and ultimately invalid are resulted, which points out that all clearances must be controlled during installation.