Abstract: Time-resolved characteristics are a very important performance parameter of GaAs photocathodes used in pump detection and other fields. In this paper, the photoelectron continuity equation and the outgoing photoelectron flow density equation are calculated by solving the photoelectron diffusion model by the matrix difference method. The factors affecting the time-resolved characteristics of the GaAs photocathode include the recombination rate of the GaAs/GaAlAs rear interface, GaAs electron diffusion coefficient and GaAs active layer thickness. Then, the effects of these three physical factors on the time-resolved characteristics of the GaAs photocathode are systematically studied. The research results show that the GaAs electron diffusion coefficient and the GaAs/GaAlAs rear interface recombination rate have a nonlinear proportional relationship with the response rate of the photocathode, and the saturation response rate of the GaAs photocathode will appear as the two increase. The thickness of the GaAs active layer has the greatest impact on the response time of the GaAs photocathode. The response time of the GaAs photocathode can be reduced to 20 ps by appropriately thinning the thickness of the active layer, which can meet the fast response requirements for most photon and particle detection. This study provides necessary theoretical support for the experiment and application of a fast-response GaAs photocathode.