Abstract: In order to solve the problem of low gas drainage concentration in high-gas and low-permeability coal seams, the influence of various characteristic parameters on the pressure relief effect in the process of hydraulic flushing in low-permeability coal seams was explored. A study on the optimization of characteristic parameters of hydraulic flushing was carried out. First, the influence of different coal output, the number of holes and the hole spacing on the effect of hydraulic flushing is studied through single factor experiments. Secondly, according to Box-Benhnken theory, 17 sets of experiments were designed, and the results were analyzed by variance to establish a suitable quadratic model. Then, the significance of the three influencing factors on the experimental results was further analyzed by response surface. Finally, the design-expert software was used to obtain the optimal combination of hydraulic flushing characteristic parameters: single coal output 0.7 t, single hole flushing times of 12, and hole spacing 8 m. A mine of Lu’an Group was selected for field industrial test. By comparing the gas drainage concentration and the gas drainage rate of the test hole and the ordinary hole in the same location, it was shown that the gas drainage volume in the test hole has been increased by more than 3 times, and the gas drainage concentration has been increased by more than 2 times.