Analysis the reasons for transient voltage of aviation generator， Based on the AC brushless generator principle, the structure diagram and the related mathematical model, the transient voltage signal is obtained by simulation of generator under MATLAB/Simulink environment. According to the relevant requirements of "GJB 1812003" aircraft power supply characteristics, The transient parameters such as voltage transients and frequency transients under the AC mode of an aircraft generator are determined, and the signals are analyzed and processed by using MATLAB, and to reduce the output delay further by zero phase filter of wave signal, and finally get the corresponding signal the AC voltage and frequency, compared to its envelope, to determine whether to comply with the relevant requirements.