Fuel flexibility is one of the most significant advantages of Solid Oxide Fuel Cell (SOFC). However, when using hydrocarbons as fuel, the degradation of cell performance caused by anode carbon deposition is one of the most important reasons affecting the long-term stable operation of SOFC. To investigate the mechanism of the influence of anode carbon deposition on cell performance, a one-dimensional transient elementary reaction kinetic model of an SOFC fueled with syngas(H2，CO，H2O，CO2，CH4) was developed. This model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure evolution, the charge and mass transport processes and the detailed evolution reaction of surface adsorbed carbon. The accuracy of the model was verified using the electrochemical impedance spectra at different moments in the reference experiment, and the mechanism of carbon deposition at SOFC anode was proposed based on the model. Under high temperature (>1 000 K) conditions, carbon is coverd on the Ni surface and Ni/YSZ/gas three-phase interface in the form of thin-film carbon, blocking the nonhomogeneous phase reaction and charge transfer reaction. At lower temperatures (<1 000 K), film carbon evolves into solid carbon, which grows inside the porous anode, blocking the anode pores and impeding gas diffusion. The constructed model can reflect this mechanism. Finally, the SOFC performance degradation due to carbon accumulation in different fuel components was investigated using the model. Study show that reducing the CH4 content in the fuel can effectively reduce the performance degradation rate of SOFCs and improve its operational performance.