Using the natural model method, an indoor natural river has been successfully portrayed with the scouring water. The experiment includes the study of the influence of different initial river geometric boundary conditions on river channel evolution process and different flow conditions. Studies reveal that flow is mostly influence to river stretcher amplitude. There are no necessary relationships among the size of the inflow angle and river''s stretcher range and the changes of river bend degrees, when the inflow angle is 300, changes of river width and curvature are the most obvious. The inflow angle affects the river evolution in a short-term and has a greater impact in the initial stage of evolution. Subjecting to initial boundary conditions, river''s evolution downward is lag and transitivity of curvature changes. Finally, this paper analyzed the sediment sorting phenomena in the process of river evolution.