The invention provides a 
coal seam step-by-step water injection precise 
control system and a water injection method and relates to the technical field of 
coal seam water injection. The 
system comprises a flow sensor, a 
pressure sensor, an injection 
liquid viscosity and pH value sensor, a 
data monitoring substation and a connection circuit, and real-time transmission of 
data monitoring is achieved. The 
coal seam step-by-step water injection precise 
control system further comprises a high-pressure water pump, a water injection 
pipe, a 
check valve, a flow control valve and an electronic 
control switch, and accurate control over water 
injection pressure and flow is achieved. The 
system further comprises a real-time mixing water tank for 
liquid injection, a plurality of injection liquid modified 
medicine tanks, a pumping pump, an injection liquid 
agitator, a steady flow control valve and a water inlet / outlet pipeline, and real-time regulation of and control over the physical properties of the injection liquid are achieved. By the adoption of the structure, based on the mechanical parameter model required for different water injection stages, a controller controls the flow of each component, and the flows are input into the PCL controller in the 
programming language, so that the real-time monitoring of and control over the step-by-step water 
injection pressure and flow are achieved, the modified injection liquid required in each stage is optimized, and the coal seam water injection disaster prevention effect is improved.