Numerical simulation was implemented on a tubular solid oxide fuel cell (SOFC) with indirect internal reformer used in the demonstration projects of Siemens-Westinghouse. The Navier-Stokes equations and the charge equation were solved by means of a generalized, threedimensional complete polarization electrochemical model for SOFC. The distributions of both the molar fraction of gaseous species and the temperature were presented. The characteristic of thermal energy generation was analyzed based on the simulation results. The electrochemical process was exothermic reaction, which contributed 82.7% in the total heat generation. The ohmic heat possessed 17.3% in the total heat generation. About 47.3% of the generated heat in the cell was absorbed by the reforming reaction. The air flow took away 36.6% the generated heat and the remainder 16% was taken away by the fuel flow.