Abstract: Underground coal gasification heat-gas co-production technology is a coal mining technology developed further from underground coal gasification (UCG), designed to achieve the full recovery and sustainable utilization of coal resources. To validate the underground coal gasification heat-gas co-production technology, this study performed large-scale physical simulation experiments to systematically investigate the spatiotemporal evolution of gas products and temperature fields during coal seam combustion. Additionally, the study explored the heat extraction efficiency of the heat-extraction pipes and its influencing factors. The results indicate that in-situ coal combustion is influenced by the oxygen volume fraction in the injected gas. An increase in oxygen volume fraction enhances both the combustion intensity and its expansion. Moreover, for every 20% reduction in oxygen volume fraction, the coal consumption rate decreases by approximately 0.83 kg/h. Temperature monitoring results indicate that the distribution of the temperature field is closely linked to both the combustion intensity and its direction of propagation. Due to the development characteristics of the microcrack network, the combustion zone in the experiment preferentially expands radially along the gas injection pipe, simultaneously shifting toward the heat extraction pipe R3. Consequently, the spatial distribution of the temper-ature field exhibits an unevenness. The gas composition analysis shows that increasing the oxygen volume fraction not only directly enhances the combustion reaction intensity and raising the CO₂ content in the gas products, but also creates a high-temperature environment that accelerates physical and chemical reactions, such as the Boudouard reaction, water-gas shift reaction, and coal pyrolysis. This increases the yields of CO, H₂, and CH₄, ultimately establishing a positive correlation between the calorific value of the gasification gas and the oxygen volume fraction. The analysis of heat extraction efficiency reveals that the efficiency is influ-enced by a combination of factors, including the spatial positioning of the heat extraction pipe, the fluid flow rate, and the pipeline structure. The pipeline R1, located close to the combustion zone, exhibits a rapid initial response and the highest average tem-perature difference (47.89 ℃) between the fluid inlet and outlet. However, pipeline R3, with a larger heat exchange area and higher flow rate, delivers higher heat extraction efficiency and cumulative heat extraction. Additionally, heat extraction efficiency is directly affected by combustion intensity, decreasing as the oxygen concentration decreases.