Based on the Armstrong model and the established electromechanical model of a Galfenol cantilever energy harvester, a nonlinear dynamic model is proposed to describe the mechanical-magneto-electro coupled characteristics of the device. Comparisons between the experimental and calculated results show that the proposed model can provide a reasonable qualitative indication of data trends, and can predict the effects of the acceleration excitation, the load resistance, and the bias magnetic field on the output performance of the device, thus has very strong practicability.Index Terms-Armstrong model, energy harvester, Galfenol, inverse magnetostrictive effect.