Abstract: In order to explore the flow characteristics of open channels with composite submerged vegetation,round wooden sticks are used to simulate rigid vegetation and plastic model grasses are used to simulate flexible vegetation. Based on the laboratory flume,water flow experiments under two layout patterns of rigid-flexible and flexible-rigid are carried out. The velocity distribution along the route,the vertical velocity distribution,the water level along the route and the relative turbulence intensity changes in the vertical direction are discussed. The results show that the flow velocity along the way fluctuates gently in the rigid area under the two patterns,and the change is greater in the flexible area,with the maximum value basically appearing at the end of the flexible area. The vertical velocity distribution in the vegetation area is basically an“S”or“C”distribution. The fluctuation of flexible vegetation is greater than that of rigid vegetation. The water level changes along the way are basically the same in the two patterns,and the water level is high under the influence of water blocking inside the vegetation. The vertical relative turbulence intensity distribution trend under the two patterns is also similar,the turbulence intensity from the bottom to the water surface increases first,then decreases and then increases. The relative turbulence intensity is the largest in the top layer of the plant.