Laser systems which operate in space environment must suffer irradiation of charging particles. Optical films are the weakest link in laser systems, and their performance and stability are easy to be affected by irradiation of charging particles. We prepared an anti-reflective film sample at 1 064 nm by Ion Beam Sputtering Deposition (IBSD), and the transmittance is 99.964 5% and the absorptance is 50 ppm at 1 064 nm. Then, used low energy protons and electrons (40 KeV) with fluencies of 1.8×10¹³ eV/cm² to irradiate the sample for space charging particles simulation. The irradiation caused a transmittance decrease of 362 ppm and an absorptance increase of 5 ppm at 1 064 nm. After thermal annealing, the optical performance of the sample was recovered. We used SRIM simulation results to analyze the experimental results, and concluded that the vacancy damage is the reason for the optical performance degradation of the film at 1 064 nm.