By analyzing the variations of the internal distributions of the temperature with time and the current density and the burnout time with the signal amplitude, we study the internal damage process and mechanism of the typical silicon-based n+-p-n-n+ structure bipolar transistor induced by three kinds of high power microwaves such as triangular wave, sinusoidal wave and square wave. The results show that the base-emitter junction is the damage position and the device is more susceptible to damage under the injection of the square waves. The displacement current and the burnout time increase but the proportion of the displacement current in the total current decreases with signal amplitude increasing. The injected power plays a determinative role in the damage process compared with the displacement current. Adopting the data analysis software, the relation equation between the burnout time t and the signal frequency f is obtained. It is demonstrated that the burnout time increases with signal frequency increasing, and the equations of the three kinds of high power microwaves all agree with the formula t= afb.