Abstract: Based on the model test, the regularity of Dongshan coal underground gasification was obtained. Air-blown gasification and oxygen-steam-blown gasification were conducted. The studies were focused on the influence of air blast on the gas composition, the influence of steam/oxygen ratio on the gas composition, gasification stability, and gasification rate. In the same time the mass balance of oxygen-steam gasification process was conducted. The results show that the underground gasification of Dongshan coal through blowing air can produce fuel gas with lower heat value, the composition of gas is influenced by the amount of air blast. Underground gasification of Dongshan coal with oxygen-steam as gasifying agent could produce synthetic gas for di-methyl ether synthesis, but moving the agent supply position is needed to keep the process going on according to the movement of fire face and change of gas composition. Mass balance can be used for prediction of gas composition. The ratio of steam to oxygen will affect gas quality and optimum steam/oxygen ratio is 1.8～2.2 for the model test. The gasification face development rate of the test coal changes gently in underground gasification process, which indicates that the underground gasification of lean coal has high stability.