A novel model of the molten carbonate fuel cell (MCFC) and gas turbine (GT) hybrid system with direct internal reforming is established, where the fuel cell and the auxiliary burner are taken as the heat reservoirs of the GT. Expressions for the power output and efficiency of the hybrid system are derived by considering various irreversible losses resulting from the overpotentials in the MCFC, the heat leakage in the auxiliary burner, and the finite-rate heat transfer and compression, expansion, and regeneration processes in the GT. The effects of some key parameters including the molar fraction of the oxygen in the oxidant, the utilization factor of the hydrogen in the MCFC on the performance of the hybrid system are revealed. It is found that the efficiency of the hybrid system will be increased by adding the utilization factor of the hydrogen, and the maximum power output of the hybrid system will be achieved when the utilization factor of the hydrogen is equal to 0.78. Moreover, the flowing rates of the syngas and oxidant and the molar fraction of the oxygen in the oxidant are determined under the optimal efficiency or maximum power output of the hybrid system. (C) 2015 Elsevier Ltd. All rights reserved.