Abstract: Aiming at the requirement of coal seam water injection monitoring automation, we proposed a solution of coal seam water injection monitoring system based on PLC structure. In this paper, the important monitoring parameters are analyzed in the automatic control of coal seam injection. The paper expounds the structure and selection of the hardware equipment of the underground coal seam water injection monitoring system. At the same time, the algorithm of the monitoring program and the communication flow of the instrument in the underground coal seam are deeply studied. The monitoring system of coal seam water injection can effectively realize the remote monitoring of the underground seam water injection.