Roll eccentricity can be compensated by disturbance control in hydraulic automatic gauge control system in strip mill, but it is hard to ensure the compensation effect what is basically open-loop control system. For this reason, a discrete assistant closed-loop system for eccentricity compensation was constructed based on closed-loop control theory. In this system, the value of compensation could be gotten from discrete access matrix according to the phase detected or calculated. The compensation deviation, which was calculated by expected value, output value and influence compensation value of former compensation value, was used to revise eccentricity compensation by the assistant closed-loop controller and to take place of the former compensation value in discrete access matrix. The assistant closed-loop system realizes rolling optimization, and improves the accuracy of thickness. Thickness system modeling and simulation analysis indicate the discrete assistant closed-loop compensation method is effective and feasible which provides a new choice for roll eccentricity compensation.