This paper introduces a new solid oxide fuel cell system using a tubular cell. We have developed a computer program for a tubular solid oxide fuel cell incorporating an inner reforming process. This program enables us to estimate the distribution of the output current density, the gas density, and the temperature distribution of bulk and gases. This program has been applied to the conventional solid oxide fuel cell power generation system proposed by Westinghouse Electric Corporation wherein the cell is cooled by air. The calculated results conform to the measured data of a test run in a 3 KW module made by Westinghouse Electric Corporation. This program has also been applied to a high speed fuel recycling system in which pure oxygen is used. Attempts to estimate the maximum current take‐out of both systems have been made. The calculations based on published data have indicated that a 300 mm cell attached to a conventional air cooling system would output an average of 370 mA/cm2 given the conditions that the fuel utilization factor is 80% and the air utilization factor is 25%. The potential between cell contacts was 0.606 V. Anything over this output is limited by the temperature tolerance of the cell. Moreover, the fuel recycling system composed of self‐supporting tubular cells was very capable of cooling under the conditions of 10% fuel utilization per cycle, 100% oxidant utilization, an average current output of 926 mA/cm2, and 0.811 V.