The complexity of the coal gas compositions and their reactions properties affect the sulfidation of H2S with calcium-based-based sorbents, which is not easy to measure quantificationally. Using the ASPEN PLUS software, the reaction degrees between coal gas compositions can be obtained easily. The results show that the thermal decomposition of H2S is affected by temperature greatly and the higher the temperature, the less stable H2S is. Adding the H2 composite will increase the stability of H2S. When the H2 molar content is higher than 2.5 %, the H2S hardly dissociate. The higher the pressure, the less of H2S decomposes. CO2 and CO both can react with H2S resulting to the decrease of H2S equilibrium concentration. The water-gas-shift reaction is the most important one among the coal gas reactions. If H2 and CO2 are present in the reaction gas, CO and H2O will appear in the off-gas largely and hence the CO and H2O compound can not be introduced to the gaseous mixtures on the experiment of H2S with calcium-based sorbents to some extent.