Abstract: For the problem of high gas coal seam in Zhongmacun Coal Mine, hydraulic flushing technology was adopted to study the hydraulic flushing and permeability increase mechanism, the optimal coal flushing quantity and optimum dip angle of hole were determined through industrial test in Zhongmacun Coal Mine by using hydraulic flushing technology. The results showed that the coal flushing quantity of single hole is floated in the range of 0.4 t/m to 1.3 t/m and the coal flushing quantity of 0.8 t/m is the majority. The inclination of drilling hole has an important influence on the coal flushing from hydraulic flushing hole and the angle of hydraulic flushing hole between 40° and 70° is best for flushing. Comparing hydraulic flushing technology with ordinary drilling, the initial extraction gas flow was increased by more than five times, attenuation coefficient was decreased by more than 50 percent.