The first three inherent frequencies and the main vibration mode parameters of the main drive system were obtained by building numerical model with MATLAB to research the vibration of the F3 rolling mill in production of CSP in Handan Iron and Steel Group Co.Ltd,and the inherent frequency which causes the main drive system resonance is determined by combining field test data.The results show that the third-order system frequency is close to the vibration frequency of the curved gear coupling between the reducer and the gear block by the on-the-spot test,and the gap of the curved gear coupling has a great impact on torsional vibration of system.Therefore,it has an important significance to reduce the curved gear coupling gap for inhibits abnormal vibration of rolling mill.