Abstract: Upper Permian in southwestern Guizhou consists of a coal-bearing sequence dominated by clastics, which can be divided into three system tracts. Lower system tract contains bay-lagoon system, middle system tract contains delta system and barrier-lagoon system,Upper system tract, clastic beach system in research area. There deposit in sealevel riffing period. Distribution of coalbed is forced to step backward to land with the rifting of sealevel fluctuation. The accumulation of main coalbed is closely related with main prograding period, main coalseams occur in the upper part of lower system tract and middle system tract. Hence, based on the transgressive-regressive cycles, the occurence of main coalseams can be effectively predicted.