In order to optimize the design of equipment, and reduce the investment in experiment expense, a large eddy simulation method coupling with 2-D unsteady VOF model is adopted to simulate the gas-liquid water-jet in and around the nozzle of pulsed anti-riots water cannon. After the setting up of experiment tape, the high-speed photography technology is adopted to photo the water jet around the nozzle, and then the velocity reader software is used to gain the velocity of the outside water-jet. Compared with the numerical result, the obtained experiment water-jet figure and velocity are in better accord with the simulation results. By using the said method to do the simulation of changing numerical parameters, the initial pressure has significant influence on the velocity of water-jet, but the initial launch angle has little influence on the velocity of water-jet, which only affect the biggest cannon-shot. The study results show that with bigger initial pressure and smaller initial water quantity, bigger water-jet velocity and shorter launch time can be obtained. The conclusion achieved is of some guide sense to the optimization of design of water cannon.