Abstract: To study the electromagnetic radiation effect of the thermal control layer covering the surface of general spacecraft in the space environment, a model of electromagnetic wave irradiated metal aluminum film material was established. The PIC (Particle-in-Cell)-MCC (Monte Carlo collisions) method was adopted to numerically simulate the changes of positive ions and collision ionization electrons under different outgassing densities. The simulation results show that when the gas density on the surface of the aluminum film is small, avalanche ionization will not occur due to the low probability of outgassing collision ionization on the surface of the material. Only when the outgassing density exceeds the threshold, the outgassing collision ionization process on the material surface is strengthened, and avalanche ionization occurs on the surface of the material to generate plasma, which absorbs electromagnetic wave energy, and the total energy of its ions and electrons increases, which may cause damage to the metal aluminum film material.