Underground coal gasification is a new natural gas development industry integrating coal mining and surface coal to gas. It is a short process, high safety and environment-friendly natural gas mining method. However, in the field test, the influence laws of different coal rock and coal quality, gasification agent type and proportion, temperature, pressure and other factors, as well as the geometric evolution laws of gasification chamber are not clear. Taking the coal seam in block a of Xinjiang Oilfield as the research object, an underground coal gasification physical simulation experimental device with a pressure resistance of 2 MPa and a temperature resistance of 1000 °C was independently developed. The distribution of combustion zones, gasification thermal efficiency and gasification composition change rules in the coal gasification process under atmospheric pressure under air atmosphere were studied. The results show that under the air atmosphere and atmospheric pressure, the components of coal to gas are H2 (6–9%), CO (16–21%), CH4 (0–1%), and the thermal efficiency of coal gas is about 16%; The coal combustion of underground coal gasification is characterized by high combustion temperature and good stability, that is, the leading edge temperature is higher than 800 degrees Celsius; Stable combustion can be maintained even when the air flux is less than 0.5l/min. This experiment will provide gasification operation control parameters for the field test and regulate the quality of crude gas pertinently.