In order to study the mechanism of high-pressure water jet on coal breaking and the popularization and application of this technology, Yungang Mine was taken as the engineering background, theoretical calculation, numerical simulation, field test and other technical means were adopted to study breaking the coal mechanism and technology application of high pressure water jet. The numerical simulation showed that with the prolongation of the action time of the high-pressure water jet and the coal body, the size of the pit bottom formed by the high-pressure water jet in the coal body gradually became larger. As the subsequent water flow increased, the energy continued to rise and would continue to the damage coal body. Field tests showed that the cumulative gas extraction volume of the borehole was about 42 598.13 m3. Compared with the previous high pressure water jet punching and hole forming, the average gas drainage concentration increased by 3.2 times, and the average extraction purity increased by 7.3 times.