In this paper, a new method for the analysis and modeling of electromechanical systems was presented, namely the Nielsen′s formulation. Nielsen′s equations of electromechanical systems can be useful for establishing equations, and have the same effect to build a model for electromechanical systems like Lagrange′s equations. According to the derivation of the equation, it can be seen that it is easier to use the Nielsen equation than to use the Lagrange′s equation in some cases. The derivation of the Nielsen′s equation for electromechanical systems is given, and the use of the Nielsen′s equation is also illustrated by examples in this paper.