According to the requirements of AGC hydraulic cylinder testbed in a certain steel mill, the AGC test cylinder loading frame and hydraulic control system were designed. Transfer function method was adopted to establish the model of the hydraulic control system, and the open loop Bodediagram of the system was got. Parameters were calculated according the hydraulic control system, and the step response curve and 20 Hz sinusoidal response curve were obtained under the condition of loading disturbance. The simulation results can satisfy the AGC hydraulic cylinder dynamic response requirements.