The influence of sulfur and metal microconstituents on air and carboxy reactivity of carbon anodes was investigated. Composite samples, simulating anodes with a range of sulfur contents, and heat-treatment temperatures were prepared for this study. Composite samples with different sulfur contents had similar physical structures but different reactivities when gasified in air and carbon dioxide. Correlations of structure with reactivity and heat-treatment temperatures for high-and low-sulfur composites were identified. The catalytic activity of metal microconstituents was found to be sensitive to the heat-treatment temperature. The results indicated that the sulfur content, interaction between sulfur and metal catalysts, and heat-treatment temperature of anode raw materials were key factors in influencing the reactivity of carbon anodes.