The transport of photoelectrons in a uniform-doping transmission-mode GaAs photocathode is calculated by establishing the models of atomic configuration and ionized impurity scattering. And the influence of the doping concentration of photocathode, the photocathode thickness, the electron diffusion length on the diffused circle and the ratio of the number of photoelectrons reaching the emit-surface to the number of exited photoelectrons at the back-interface of GaAs photocathode are analyzed. The calculated results show that the limiting linear resolution is 769 mm-1 with the cathode thickness being 2 m, the electron diffusion length 3.6 m and the uniform-doping concentration 11019 cm-3. The research on the transport of photoelectrons is worthwhile for preparing the high-performance GaAs cathode and improving the resolution of intensifier image.