The magnetostrictive sensor (MsS) of guided wave is a new type of ultrasonic testing device used for the structural health monitoring (SHM) of systems. Its use can be limited by its shortcomings: It has low signal to noise ratio, and its output is affected by the nonlinear magneto-mechanical coupling performance under a magnetic field. In order to solve these problems, a dynamics mechanical model is set up for MsS guided wave generation on the nonlinear magneto-mechanical coupling performance of ferromagnetic material. The effects of the bias magnetic field, excitation frequency, and excitation current on the particle amplitude are analyzed. The dynamics mechanical model is verified with the FEM method. The difference in particle amplitude between the nonlinear and linear model is discussed, which further proves the model′s applicability. The results indicate that low frequency, heavy current,and suitable bias magnetic field can improve the conversion efficiency of the magneto-mechanical coupling performance under conditions of considering dispersion. The suitable bias magnetic field is determined by the maximum tangent slope of the amplitude curve.