Abstract: While designing hydraulic servo Control system we usually do the best to avoid tie influence of pipe effect, However, in this paper we deal with the application of pipe effect to Correct the pressure Control system in the bending-Roii hydraulic system of rolling mills. Through the analysis and experiments in the four-high rolling mill we abtained the evidences that with this method the bandwidth of system Can be Spread effectively, So it becomes the new simple and reliable meathod to raise the remsponse of system greatly.