To investigate the performance of an irreversible direct ammonia-fed solid oxide fuel cell, the direct ammonia-fed solid oxide fuel cell based on oxygen ion conductivity was modeled using finite time thermodynamic theory. First, mathematical expressions for the output power, output efficiency, ecological objective function and ecological coefficient of performance of the direct ammonia-fed solid oxide fuel cell were derived. Further, the effects of parameters such as operating tempera-ture, operating pressure, fuel utilization, and electrolyte thickness on the performance of direct ammonia-fed solid oxide fuel cell were numerically investigated. The results show that as the operating temperature of direct ammonia-fed solid oxide fuel cell increases, the performance of direct ammonia-fed solid oxide fuel cell including output power, output effi-ciency, ecological objective function and ecological coefficient of performance will be improved. Under certain conditions, increasing fuel utilization can improve output power, output efficiency and ecological performance. Increasing the elec-trolyte thickness will decrease the finite time thermodynamic performance of direct ammonia-fed solid oxide fuel cell. Moreover, the microstructure of the electrode also affects the performance of direct ammonia-fed solid oxide fuel cell, and the ecological objective function is increased by 16.9% when the electrode porosity is increased from 0.4 to 0.8.