The Finite Element Method was combined with the results from considerable analysis, producing a new kinetics analysis method of EFEM for a mechanism in truss, geared system, and assembled system. The equivalent principle and the motive differential equation of the system were derived by using an equivalent element, a virtual inertia matrix, and a systematic force matrix. The element' s mass matrix expression in the two dimensional and three dimensional mechanisms of the equivalent element was determined. The equivalent mass matrixes fashion of the Jacobin matrix, generalized coordinate matrix, and equivalent forces matrix were also determined. It was validated by two examples that the new method was normal, simple and direct, and had a higher efficiency than alternative methods; this is regardless of whether traditional methods are used with differential equations and calculated by using a computer.