A new method for calculating product gas composition and coal consumption rate from a ＇＇channel type＇＇ underground gasification process has been developed. The model comprises radiant heat exchange between channel walls and natural-convection-driven mass transfer within a section of the channel. The model is used to demonstrate the influence of operating conditions such as pressure, air injection rate, and water injection rate on product gas composition. Model predictions are, furthermore, compared with observations from field trials.