Water injection dredging (WID) has been widely used as a new dredging and leveling tools.Accurate calculation of pipe pressure loss and nozzle flow intensity is directly related to the type of ship pump selection and dredging effects. Three computational models are established by changing the shapes and distributions of the nozzles, the flow resistance and nozzles flow intensity of which are compared, analyzed and evaluated respectively. The calculated results show that the pressure loss in pipes of truncated cone shaped nozzles is smaller than that of cylindrical nozzles. Besides, the nozzle flow intensity is related to the speed and thickness of the layer in the process of dredging. We can change the nozzle flow intensity for better cleaning results.