Carbon deposition has a serious effect on the performance of solid oxide fuel cells (SOFCs). An unsteady-state 2D model based on COMSOL software is used to study the carbon deposition process in a planar SOFC. The carbon deposition, catalyst activity, reaction rate and temperature fields are obtained to analyse the mechanism of carbon deposition in the SOFC at different operating time. The effects of the operating voltage, inlet H-2 molar fraction, operating pressure and operating temperature on the performance of the SOFC are investigated in detail. It is found that the biggest variation of the performances caused by carbon deposition occurs in the inlet domain of the anode support layer. The increase of operating voltage, inlet H-2 molar fraction, operating pressure and temperature accelerates the carbon deposition process. The predicted results could deepen our understanding of carbon deposition and its transient quantitative effects on the catalyst, structure and cell performance. (C) 2014 Elsevier Ltd. All rights reserved.