As one of the most important energy sources, coal can be gasified to syngas in order for it be used in solid oxide fuel cell (SOFC) efficiently and cleanly. However, the big challenge of the utilization of the syngas in SOFC is the carbon formation activity in the Ni/YSZ anode. In this work, according to the fully three-dimensional models of chemical/electrochemical, heat/mass transfer and overpotential, the effects of fuel components on the performance and carbon formation of SOFC were analyzed. From the results, the increment of water steam and carbon dioxide may inhibit the carbon deposition. However, massive water steam and carbon dioxide reduces the output voltage of SOFC as well. The proper molar fraction of hydrogen in syngas also reduces the carbon formation activity. The addition of carbon monoxide may narrow down the region of carbon formation but enhance the carbon formation activity near the fuel inlet of SOFC. Moreover, the existence of methane results in the sharply carbon formation; thus, the methane should be removed as clear as possibly in syngas.