Abstract: The commutation phenomena produced by anode outgassing ionization and secondary electron emission are a possible factor to limit the performance of the transparent cathode relativistic magnetron with all cavity axial extraction (TCMAC). In this paper, physical modeling technology of the high-power microwave device TCMAC anode outgassing ionization phenomena and three-dimensional particle simulation are analyzed. The outgassing ionization and secondary electron emission can reduce the output power. When the number of positive ions is greater than that of electrons, the plasma caused by the ionization will make the microwave output power decline rapidly and cause system breakdown.