Abstract: The key of the technology for pressure relieving drainage lies in decorating gas extraction hole reasonably based on the distribution rule of mining-induced fractures field. Aimed at thick coal seam enriched in water for large mining height and rapid development, on the basis of the characteristics of space-time evolution of mining-induced fractures and gas migration rule, the commercial test of the technology of pressure relieving drainage for reasonable horizon was confirmed in Nanting mine. According to the statistical analysis of different extraction concentration, the effect for end hole of pressure relieving drainage hole in the extraction zone of fissure zone was the best, so the reasonable horizon of pressure releasing gas drainage hole was determined.