Abstract: Based on the computational fluid dynamics, a three-dimensional model is established for numerical simulationof the flow field around a pipe stopper when it plugs the pipe. The distributions of the velocity vector, the particle velocityof the fluid and turbulent kinetic energy before and after the plugging are obtained. The simulation results show that theprogress of the plugging operation has an impact on the distribution of the particle velocity and the turbulent kinetic energy, the mechanical structure of the pipe stopper causes vortexes of the fluid at some location and the tail-end, and forms aturbulent flow in the pipeline, which has an impact on the plugging performance. The research results give guidance on safeplugging and the structure design of the pipe stopper.