Aiming at the problem that the current theoretical models for calculating the resolutions of low-light-level image intensifiers are not accurate enough and can’t provide the optimization conditions intuitively， a theoretical model based on electron tracking is proposed. Electron scattering formula of uniform-doping GaAs photocathodes is used for obtainig the distribution of emitted electrons， which is different from the Lambertian distribution. The proximity system is approximated to a longitudinal uniform electric field to establish the electron transport model. Based on the secondary electron emission distribution， the electron transport model in the microchannel plate is established under non-abnormal working conditions. With the distribution of the electron beams on the phosphor screen， the modulation transfer function is calculated by Monte Carlo method， and the limiting resolution is obtained by taking the standard value as 0.3. The resolutions of four different types of image intensifiers are calculated， and the results show that the largest error between the model simulation results and the experimental results is only 5.0%， less than the errors from the existing models（more than 10%）， which proves the practical value and good application prospect of the model.