A directional water pressure blasting method for improving coal bed gas permeability includes utilizing water pressure blasting splitting to change the structure of the coal and rock mass, firstly drilling holes inside a coal bed, performing high-pressure hydraulic cutting seam, and forming a deep flat slot around the drilling holes of the coal bed after cutting; and filling explosive into the drilling holes of the coal bed, then injecting water and sealing the hole, detonating the explosive to perform water pressure blasting, and enabling the periphery of the drilling holes of the coal bed to generate directional expanding fractures under the function of detonation pressures. Performing water pressure blasting in a high-gas low gas permeability coal bed can organically combine the waterpower and the explosive force of the explosive fully and reasonably, the water pressure blasting enables the cracks generated by hydraulic cutting seam to further expand and a directional expanding cross fracture net is formed on the periphery of the drilling holes of the coal bed, so that the gas permeability of the coal bed is greatly improved, the problem that the gas of the coal bed is hard to extract due to the small number of the cracks can be effectively solved, the concentrated stress of the coal bed is transferred to the deep of the coal mass, and the capacity of gas emission is improved. The directional water pressure blasting method for improving the coal bed gas permeability is simple in process, convenient to operate, safe, reliable, and good in controllability and effects.