Abstract: As an excellent photoemission material, GaAs is widely used to prepare cathode materials.Gallium arsenide is usually driven by 532 nm CW laser, which has much lower peak power than the nanosecond pulsed laser at the same average power. Therefore, high peak power laser irradiation can not be avoided when there is a need for some supercharges. Therefore, in the process of using GaAs cathode, it is necessary to measure its damage threshold.Based on the above background, the laser damage threshold of GaAs material is first obtained by calculation, then verified by software simulation. Finally, the difference is analyzed and compared with the experimental results. The numerical result is 17.811 MW/cm², the simulation result is 19 MW/cm², and the experimental result is 13.5 MW/cm². After reasonable analysis, it is believed that the damage threshold of GaAs as photocathode material will be further reduced.