Abstract: Abstract: Northeastern Yunnan has rich resources and hence serves as a major coal resource base area in southwestern China. Based on previous researches in the study area, the authors made a comprehensive analysis of field geology, mountain projects and drilling data and, on such a basis, investigated the variation regularity of mineable coal seams in major Upper Permian coal-bearing strata. The results show that, spatially from east to west and temporally from early Xuanwei to late Xuanwei, the mineable coal seams are uplifted and tend to ‘migrate’ from the bottom upward. An analysis of the factors responsible for such variation regularity and the variation of the ancient geography from west to east shows that the gradually stabilized structural conditions and periodic eustatic sea level jointly control the distribution and ‘migration’ of the mineable coal seams. In addition, the mineable coal-seams and mineable segments in different places are pointed out, which is of practical guiding significance for the exploitation of the coal resources in the study area.