Punching mechanisms with servo input are typical variable-input controllable mechanisms. By means of extending the output link infinitely, the Stephenson Ⅲ six-bar linkage is evolved into a six-bar punching mechanism with a slide. A virtual prototype model of this novel punching mechanism was established by using the software ADAMS. The model includes geometry, load and drive, total three sub-models. Based on the model, the kinematic and dynamic characteristics of the slide with variable-input crank motion and instantaneous large load were simulated. The numerical results showed that the Stephenson’s six-bar punching mechanism had good transmission characteristics, improving the working performances and production efficiency, reducing the manufacturing costs of servo mechanical presses.