Water jet is widely used in dredging engineering, it can clear away the sediment and break the compact soil under water. Therefore, it is necessary to study the jet scour. The sand bed with the median particle size d50=1.8mm is selected as the research object. For obtaining the relationship between jet distance h and the scour, the Sediment Scour Model is used to simulate the erosion. The numerical simulation results are found in good agreement with those obtained from the experiment. They indicate in the early stage of the scour, the scour depth εm decreases with the h increasing. In the late stage of the scour, εm first increases and then decreases with increasing of h.