Abstract: The multi-physics simulation algorithm is employed for analyzing the damage of semiconductor devices when high power microwave is injected. The principle and procedure of the multi-physics simulation is briefly introduced. The expression of the carrier ionization rate in the equations of semiconductors physical model is introduced to simulate the avalanche breakdown within Schottky diode. The multi-physics simulation is employed for the analysis of ionization effect and avalanche breakdown of HSMS-282C Schottky diode. The accuracy of the method is validated through comparison of its simulation results with the measurement data. The method can provides useful physical mechanisms for better understanding of the behavior avalanche breakdown within diode.