Abstract: Taking the coal reservoir in the Aiding Lake Area of the Tuha Coalfield as the research object, the characteristics of coal, rock, coal quality, coal seam occurrence, hydrological features, surrounding rock properties, and geological structural characteristics are systematically analyzed. Mathematical analysis methods such as the analytic hierarchy process, coefficient of variation method, and TOPSIS method are adopted to establish a geological layer-selection resource evaluation system for underground coal gasification. The feasibility of underground coal gasification in the Third Area of Aiding Lake in the Tuha Coalfield is investigated, and favorable zones are identified. The results show that the study area has a gently inclined monoclinic structure with undeveloped faults; the coal seams have a simple structure, stable medium thickness, low ash and moisture content, and moderate burial depth; the roof and floor are mostly composed of fine sandstone, siltstone, and mudstone. Overall, the area is suitable for underground coal gasification. On this basis, 19 geological influencing factors—including coal seam thickness, burial depth, and inclination—are further selected as secondary evaluation indices. Their comprehensive weights are calculated and graded, and the combined weights of each secondary index are determined. The fuzzy mathematical comprehensive evaluation method is applied to conduct quantitative evaluation and geological selection for the No. 6 coal seam in the Third Zone. Two favorable areas and two more favorable areas are identified, which provides a scientific basis and strong support for the subsequent implementation of underground gasification work in this area, and also has reference significance for geological site selection of underground coal gasification in other regions.