Abstract: Applying a reversible linear transformation and a near-identity nonlinear transformation with parameters, the simplest normal form of an electromechanical coupled nonlinear dynamic system was developed. Furthermore, its universal unfolding and the relationship between parameters of this system and those of the original system were also obtained. The codimension-two bifurcation was analyzed and the effect of each parameter on the dynamic behavior of the system mentioned above was revealed, which laid a theoretical foundation for parameter design, stable operation and fault diagnosis of a real system. The numerical simulating result of the electromechanical coupled nonlinear dynamic system was obtained, which verified the corresponding theoretical analysis result.