Based on in situ DRIFTS studies of ammonia storage mechanism over the Cu-SSZ-13 catalyst, a temperature-dependent heterogeneity constant was introduced in the traditional dual-site model, and was compared with traditional dual-site and multi-site models based on a series of NH₃-TPD experiments in this work. The results showed that the modified dual-site model was in better agreement with experimental NH₃-TPD measurements than the traditional dual-site model, and even better than the multi-site model at some temperatures. Moreover, the modified dual-site model was validated under transient conditions with different adsorption concentrations, flushing durations and heating rates. The results showed that the model predicted the NH₃-TPD process well under these transient conditions. The accuracy was better than that of the traditional dual-site model, and comparable to that of the multi-site model. The modified dual-site model had similar accuracy, but less parameters compared to the multi-site model, and the reduced model complexity is of great significance for the model-based urea injection control of diesel engines.