To study the change rule of water hammer pressure produced by pressure pipes after rock plug blasting in a water intake project, based on the method of characteristics, the one-dimensional transient flow theory and the working principle of actual blasting, a mathematical model of rock plug blasting in a water intake for water conservancy projects is established combined with the requirements of pipeline safety control. The results of numerical simulation show that the pressure in the pressure pipeline fluctuates greatly after blasting, and the negative pressure is easy to cause water hammer of cavities collapsing accidents under the vaporization pressure. Therefore, additional water hammer protection measures are needed to ensure the pipeline safety. Increasing the area of the shaft can reduce the extreme value of the water hammer pressure, and the larger the area of the ventilation shaft, the smaller the pipe pressure. When the shaft diameter increases to 10. 0 m, the negative pressure value can meet the requirements.