Solid oxide fuel cells (SOFCs) can directly utilize solid carbon as fuel by integrating with the reverse Boudouard reaction in the anode chamber. Efficiency of the Boudouard gasification of solid carbon fuel is one of the crucial factors influencing the performance of direct carbon SOFCs (DC-SOFCs). In this paper, a novel Boudouard reaction catalyst derived from steel slag was first introduced into DC-SOFCs for improving the electrochemical performance. The catalytic activity of the steel slag was activated using the molten alkali method to decompose the inert mineral phases of the raw material. The steel slag-derived catalyst was loaded on the activated charcoal by a wet ball milling method. This kind of catalyst can match up to the readily available solid carbon fuels in cost. Promoted by this highly active Boudouard reaction catalyst, the initial Boudouard gasification temperature of the carbon fuel decreased by 99 degrees C, and the producing rate of carbon monoxide doubled. Furthermore, the power outputs of the fuel cells increased from 91 to 159 mW cm(-2), and the fuel utilization increased from 17.10% to 46.43% at 825 degrees C. This study demonstrates that the steel slag-derived catalyst is a promising material for the performance improvement of DC-SOFCs and may make a valuable contribution to their commercial application.