Performance test rig of the electric nail gun consists of five parts and the key one of which is the loading mechanism. By analyzing its working principle, virtual prototype model of the loading mechanism was established using simulation software ADAMS. Through simulation of the prototype model, the design requirements of the loading mechanism were given. Then, using the method of parametric analysis, dynamic characteristics of loading mechanism was obtained. Eventually, the relationship between the preload force of loading spring and the implanted force of the sample nail was presented.