Abstract: The effects of alkali and alkaline earth metals (K, Ca) on the steam gasification of a lignite char were investigated with a fixedbed reactor. The gasification reactivity of the chars with different catalyst loadings was examined. The crystallite constituents in the char and its gasification residue were identified by Xray diffraction (XRD). The morphology of the chars and the catalyst dispersion were analyzed by scanning electron microscope (SEM) equipped with an energydispersive Xray analyzer (EDX). The results show that the catalytic effect of potassium is higher than that of calcium. The reactivity of chars increase linearly with catalyst loadings up to a loading saturation level (LSL) which is about 10% for both K and Ca. K and Ca were identified by EDX on the surface of chars produced from the raw coal samples loaded with potassium carbonate and calcium nitrate respectively. Gehlenite is the major constituent in the gasification residue of raw char. Gehlenite and rankinite are the major crystallites from chars loaded with potassium carbonate and their residues, but the crystallite with K is not detected by XRD. Large amount of calcium oxide attached to the char surface and the catalyst dispersion deteriorates due to agglomeration when the calcium loading is above the LSL. In addition to gehlenite and larnite, calcium oxide and calcium hydroxide uncontaminated by mineral matter are detected in the gasification residue from char loaded with 10% calcium.