Abstract: Aiming at the problems of long roll changing time and low reliability of roll changing device in the continuous cold rolling production line at present,the structure and principle of work roll changing device of 4-high skin pass mill were introduced. Through comprehensive analysis of work roll changing steps and time sequence, some of the series operation steps were optimized to parallel operation or lap operation. It was found that the key factor affecting the work roll changing time was the running speed of AGC cylinder, and then the servo hydraulic system was optimized with constant power pump characteristics to improve the running speed of AGC cylinder and greatly reduce the work roll changing time. In order to improve the reliability and stability of the work roll changing device, the structure design, the selection of detecting elements and the installation accuracy of the device were optimized and improved. After adopting above measures, the work roll changing time is greatly compressed from more than 120 s to less than 90 s, and the operation reliability and stability are significantly improved, which lays a foundation for the continuous and stable production of the cold rolling production line and the improvement of product quality.