The purpose of this work is to investigate the synergistic catalysis between calcium species and K2CO3 for the char gasification. Graphite and four mineral-free chars including an anthracite coal char, a bituminous coal char, a lignite coal char and a pine wood char were gasified at 750 degrees C in a stream of steam/argon under atmospheric pressure. It was found that each of three calcium species (Ca(OH)(2), Ca(CH3COO)(2) or Ca(Ac)(2), and CaCO3) synergistically promoted the catalytic activity of K2CO3 for the gasification of all samples, and the extent of promotion was dependent on calcium species and carbon or char samples. The formation of a eutectic from the calcium species/K2CO3 catalyst was proved to be an important mechanism for its better catalytic effect. The presence of the organically bound calcium on the char was also likely to be responsible for the promoted catalytic gasification. (C) 2013 Elsevier Ltd. All rights reserved.