To study the effects of various factors of a submerged vertical jet on sediment scour process，a jet scouring test system has been designed and built based on the “semi-model” theory. Through image capturing and processing technique，variations of the scour hole shape with the scour parameter EC are obtained，which takes into the account the influence of jet velocity，target distance and nozzle diameter. The results show that initially the scour hole depth increases rapidly and then increases slowly towards reaching equilibrium state，during this process，the shape of the scour hole maintains geometric similarity. The size of the scour hole increases with the increase of jet exit velocity，whereas the dynamic scour hole depth is significantly greater than the static scour hole depth. In addition，the optimum jet target distance is obtained through the tests，at which the depth of the scour hole reaches the maximum. The results can provide useful reference for the practical engineering application of jet dredging.