A comprehensive mathematical model was established by considering the main and side reactions for solid-state polycondensation of poly(ethylene terephthalate). The effect of temperature on chain mobility was used to estimate the rate constants of chemical reactions. The polymer crystalline fraction was modeled as containing only repeat units, thus concentrating end groups and condensates in the amorphous fraction. The diffusion coefficient of acetaldehyde was calculated by the model. The simulation results of this comprehensive model were validated by experimental data reported in literature. The model predictions were important clues for further experimental study on poly(ethylene terephthalate) solid-state polycondensation.