In view of the excessive local control conditions, the power of the cam curve designed by traditional polynomial interpolation method got too high to control, which was not conducive to the processing of capping machine cam. The global 5, 6 and 7 polynomial fitting methods were separately used to design the cam curve, so that it could control the power of the polynomial while satisfying the local control conditions. When the parameters of the cam curve got optimized, constructed the cam mechanism into a three-dimensional model and carried out the dynamic simulation analysis. After comparing to the kinematic and dynamic properties of mechanism, finally the optimal curve was determined.