Zirconium diboride (ZrB₂), a thermal protection material for hypersonic vehicle, has received widespread attention in recent years. Here we advance an oxidation model based on oxidation products (ZrO₂ and B₂O₃) and their morphology at different temperatures to simulate the oxidation behavior of ZrB₂. This study further establishes the dynamic equilibrium among formation, evaporation and supplement of B₂O₃ whose concentration at ambient was assumed to be nonzero. Research results indicate that the advanced model can predict the oxidation behavior of ZrB₂ under quasi-static low flow conditions and the simulation results are consistent with the data obtained from sample suspended in wire heater furnace at constant temperature. The porosity has a great influence on the oxidation process, and at the same temperature and oxygen partial pressure, the larger the porosity, the higher the oxidation degree. The oxidation rate controlled by diffusion in the presence of liquid B₂O₃ film laying outer surface of substrate reduces greatly and the material exhibits the strongest oxidation resistance.