Abstract: In order to clarify the geological factors affecting underground coal gasification（UCG） of closed coal mines and build a scientific and systematic geological index evaluation system, in this paper, we take a typical close coal mine in Hebei Province as a study case to establish an evaluation system of geological conditions. This evaluation system systematically analyzed and quantified 4 first-level geological indexes and 22 second-level geological indexes, corresponding to the several stages from planning to production of UCG. By using analytic hierarchy process and fuzzy comprehensive evaluation method, the importance matrix of evaluation index is established and the index weight is determined. Combined with the actual situation of too little remained resources, extremely complex coal seam structures and excessive water inflow, the evaluation result is one-vote veto, and a set of scientific and systematic geological index evaluation system is finally formed. The application of the evaluation system in typical closed coal mines in Hebei Province（coal seams 8-1, 11, 12, 14 in Linnancang Coal Mine, coal seams Ⅲ₃, Ⅴ₂ in Xuandong No.2 well, coal seam 5 in Beiyangzhuang Mine, coal seams 1, 5, 6 in Cuijiazhai Mine and coal seams 1, 9 in Xiandewang Mine） ｓhows that it is suitable for UCG.