To explore the correlation between the performance of direct carbon fuel cells and the characteristics of semi-coke as the fuel, a strategy for adjusting the characteristics of semi coke is employed by changing the coal pyrolysis conditions. It is found that the ratios O/C and H/C of semi-coke are decreased with an increase in the final pyrolysis temperature, a slowing of the heating rate and an extension of the pyrolysis residence time. In addition, CO2 activation can increase the specific surface area of semi-coke. The performance of a direct carbon fuel cell increases with an increase in O/C and H/C in semi-coke. Meanwhile, the combustion characteristic index of semi-coke has a linear correlation with the maximum output power of a direct carbon fuel cell, so the combustion characteristic index can be used as a reference indicator for a direct carbon fuel cell to select solid carbon fuel. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.