Abstract: Based on the concepts of irreversible thermodynamics, a model for ther-modynamic analysis of ammonia synthesis reactors has been proposed. This model was checked by availability analysis of classical thermodynamics and calculation showed that the model gave good accuracy. The method is characterized by its ability to classify various kinds of exergy losses and to correlate these losses to effects of kinetic factors. Various types of ammonia synthesis reactors were evaluated by means of the proposed model.