Considerring flow field features of J41H- stop valve in the working state working for XYZ-125G Lubricant Machine, a flow situation of stop valve using CFD method is performed. The parameters of velocity, pressure and pressure head-loss will be given by details when stop valve opening and closing. The pressure head-loss values of CFD simulation is in good agreement with the one of theoretical calculations, the manipulation including opening or closing stop-valve and oil-pump’s stopping suddenly will change oil particle’s velocity accompany with pressure fluctuation. Flow phenomenon such as Whirlpool, water hammer, and stagnant water zones can be observed from the CFD analysis results which Provides a theoretical basis for Valves structure optimization and Prediction and Prevention for hydraulic shock.