The invention discloses a coal seam water injection system which comprises a pulse power subsystem and a water injection subsystem, wherein a water outlet of the water injection subsystem is communicated with a coal seam to be subjected to water injection of a set area so as to inject water into the coal seam to be subjected to water injection; and a liquid outlet of the pulse power subsystem is communicated with the coal seam to be subjected to water injection of the set area so as to provide hydraulic pulse to the coal seam to be subjected to water injection. According to the coal seam water injection system, the water injection of the coal seam with poor air permeability can be effectively realized, and the coal seam water injection system has the advantages of simple water injection operation and good effect.