Magnetic acoustic emission (MAE) is an important non-destructive testing method commonly used to evaluate the mechanical properties of ferromagnetic materials. However, there are few reports on the theory or numerical models of MAE. A theoretical MAE model considering the microstructure ( dislocation density and grain size) is proposed in this paper. The influences of magnetization parameters and microstructure parameters on the envelope of MAE signal are analyzed through numerical calculations. After that, the rationality of the MAE model is validated. Based on the MAE predicted signals with different hardness specimens, the dynamic hysteresis parameters and magnetized structural parameters in the theoretical model were inverted with the genetic algorithm. The results demonstrate that the MAE signals calculated from the theoretical model under the inversion parameters are in good agreement with the experimental signals, and the maximum error between the inversion values of the key hysteresis parameters and the theoretical calculation results is less than 15% . Therefore, the theoretical model can be used to predict the MAE signals.