The punching mechanism was an efficient automatic forming equipment. There were many researches on the structural parameter’s optimization design, motion analysis and characteristics of the punching mechanism. However, there was relatively little dynamic analysis of the new punching mechanism. In order to expand the application of the punching mechanism, an optimized planar punching mechanism with one-DOF and two-slider output eight-bar was proposed. The mechanism had symbolic kinematics and contained three sub-kinematic chains (SKC), of which the inverse dynamic analysis was performed. Firstly, using the principle of structure coupling-reducing, a two-slider plane punching mechanism with zero coupling degree and single degree of freedom was optimized and designed. The topological structure was decomposed and the coupling degree of mechanism was declined to be zero (κ=0). Therefore, it was easier to obtain the symbolic forward position, velocity and acceleration. Then, the basic principle of the ordered single-open-chains (SOC) method based on the Newton-Euler principle, which was proposed by the author’s team, was introduced, the force analysis of each component was carried out. And the inverse dynamic modeling of the mechanism was established to obtain the dynamic supporting force and driving torque of the mechanism. Finally, the inverse dynamics modeling of punching mechanism was established by using the Lagrange equation, and the errors between the N-E’s SOC method and the Lagrange method were compared, which indicated that the former had high modeling accuracy. The research result provided a theoretical basis for the popularization and application of the SOC-method based on Newton-Euler in mechanisms that contained some SKCs and the strength analysis and dynamic performance optimization of the punching mechanism.