Abstract: In order to reduce an engineering quantity of the gas drainage borehole in low permeability seam and to improve the gas drainage efficiency,a study was co nducted on the permeability improvement theory and technology application in a low permeability seam.Based on the controlled hydraulic fracturing conception of the sea m,a hydraulic fracturing numerical simulation in the underground mine and the optimized design software were developed and a sealing method of a high pressurized upwa rd borehole and horizontal borehole was provided.Thus the key technology to detect the fracturing water distribution scope was developed and the site application was con ducted.The results showed that with a target,orientation and regional fracturing to realize a permeability improvement of the target regional seam,in comparison with the be fore and after the controlled hydraulic fracturing,the single borehole gas drainage volume was improved over five times,the gas drainage borehole engineering workload wa s reduced by 1 1 3 in some coal mining face,a single day coal production and driving rate of the gateway driving face was highly improved.The controlled hydraulic fracturin g in the underground mine was an improvement and innovation of the conventional hydraulic fracturing technology and could effectively promote the seam permeability imp rovement in the target region and could improve the gas control effect.