Aiming at the problems such as low positioning accuracy, low rolling accuracy and unstable operation process of the three-roll coiling machine driven by the hydraulic system,the mathematical model between the rise of the lower roll and the radius of the rolling,the thickness of the plate and the property of the material was established on the basis of the three-roll coiling forming process and the structure of the three-roll coiling machine adjusted horizontally.Based on the mathematical model and the feedback of lower roll position,a closed-loop system of lower roll positioning was established,and a control system with Siemens S7-1200 as the main controller was developed.The experimental results show that the precise control of lower roll positioning is realized,and the forming precision and working efficiency of the coil are improved by driving the lower roll up and down by servo motor.