Abstract: Hydraulic screwdown roll gap regulating device is used on cross wedge mill.Based on the Popov-Landau's ultra-stability thorem, a kind of electrohydraulic servo model reference adaptive control system is introduced. The paper gives the algorithm, design method, theoretical analysis and digital simulation results,which shows that this controlled system has good static and dynamic characteristic.The simulation results of the MRAC system proposed here also show good following and anti-interference ability.The form of the controller is easier for field use.