Abstract: The catalytic effect of calcium component on steam gasification of Shengli lignite char was studied. Demineralized coal samples were loaded with calcium oxide and pyrolyzed at 1 100℃ (Ca-J). Ca-J⁺ was prepared from Ca-J treated by hydrochloric acid. The char samples were characterized by BET, SEM-EDS, XRD, FT-IR and XPS. The steam gasification of the char samples was performed in a micro fixed bed reactor. The possible catalytic active micro structure was discussed and proposed. The results show that carbon conversion and reactivity index of Ca-J and Ca-J⁺ samples during steam gasification were substantially similar, but much higher than those of demineralized char samples (SL⁺-J). Ca (CH₃COO)₂ and Ca-OOR, two calcium species are present in Ca-J⁺ sample determined by XPS. Chemical analysis and SEM-EDS prove that calcium content of Ca-J⁺ decreases by more than 97% than that of Ca-J sample. XRD analysis indicates free inorganic mineral (CaS, CaO) is removed by hydrochloric acid. FT-IR spectra show C=O, C-O peaks present in Ca-J and Ca-J⁺ samples. So it is postulated that "R-O-Ca-O-R'" (R and R' are aliphatic and aromatic structures, respectively) is the catalyst active microstructure during char steam gasification.