The main objective of this research was to comprehensively investigate the role of the hot blast furnace slag (BFS) played in coal gasification reaction process so as to improve the utilization of BFS waste heat and enhance H 2 and CO content in the syngas. The BFS characterizations, such as the heat carrier, catalyst, reactant, and the sulfide capacity were investigated. The results indicated that about 61% BFS waste heat could be recovered by coal gasification, and the exergy loss (EXL) of which was only 409 MJ•t-1 slag. Therefore, the BFS was the favorable heat carrier for coal gasification reaction. Besides, the activation energy (E a