Abstract: In order to solve the problem that excessive axial force causes a displacement accident of the main motor bearing box and horizontal axis bearing box in the drive system of a 2250 hot continuous rolling R2 rolling mill, an on-line monitoring system of axial force was developed to monitor the axial force for a long time on-line. The main reason for axial force generation was theoretically analyzed and a computer simulation was carried out. It is shown that the axial force is closely related to the roll cross angle, and can be effectively controlled by reducing the gap between roll bearing box and the arch. This result was verified by field experiment.