Regarding the problem that how to set jet target distance to improve scouring capacity and reduce energy consumption in engineering practice,we carry out a numerical simulation study.Taking fine sand with a median particle size of 0.13 mm as the research object,we build a moving jet scouring model,and verify the reliability of some parameters chosen by comparing with physical test outcome.Then we use this model to simulate vertical submerged jet scouring on fine sand,and analyze effects of target distance on scour depth,productivity and specific energy of jet.The results show that with the increase of moving jet target distance,scour depth first increases and then decreases.Sour capacity first increases and then decreases,while scour specific energy first decreases and then increases.An optimal target distance exists with limited energy consumption but high scour capacity.