Abstract: The model investigations of the vertical vortex at a horizontal intake are performed by a self made model.The particle movement at the surface of the vertical vortex is traced by a color pigment,which shows the moving trace is a multi-circle helical flow. According to the characteristics,the average tangential and axial velocities are obtained by the photography method and the image processing technique By comparison with the theoretical results,the simple and economic means is proved to be feasible.The influence on the vertical vortex formation of different approaching directions is also analyzed,and the result shows the oversize angle between the intake axis and the approaching direction is a factor of the vertical vortex generation.The formulas of the critical depth of submergence of different approaching directions are obtained by the measured data, and the formula is extended for the reference of the design.