Abstract: Based on the motion equations of rolling mills, the relation between the parameters of an automatic gauge control system and Smale chaos and the effect of chaos existing in the automatic gauge control system on the control precision were analyzed through discussing the homoclinic orbit and the Melnikov function. The condition that Smale horseshoe chaos occurs in the automatic gauge con-trol system was given. A new idea was proposed and verified that roll eccentricity disturbances on gauge control is chaotic during roll-ing. Simulation results show that the thickness deviation of the rolled will be large when chaos occurs and the product quality can be improved by chaos control.