Aiming at the frequent shutdown of the roller bearing on the backup roll of a straightening machine in a steel mill in China, the failure condition of the bearing was introduced. The bearing copper retainer was severely worn and fractured. The side flange of the inner ring was seriously worn and the other side was slightly worn. The end face of the roller was badly worn. The cause of bearing failure was analyzed. It was considered that the bearing was subjected to a larger axial force due to the deformation of the backup roll. And other reasons that might cause great axial force were also analyzed. The optimization scheme was to change the CA type spherical roller bearing to CC type, and the advantages of the CC type bearing were explained.