In the experimental study on vertical distribution of flow velocity in double layer vegetated channel, PVC cylindrical rods are simulated as a rigid vegetation. Three-dimensional ultrasonic Doppler speedometer ADV is used to measure velocities in different locations of the rectangular flume. The results show that:(1) the velocity profile behind tall rods exists four inflection points that divide the velocity profile curve into five parts. And the flow characteristics of each part are not identical. (2) the velocity profile behind short rods existes three inflection points that divide the velocity profile curve into four parts. The shapes of velocity profile between the height of tall rods and short rods are different and other parts are generally similar.(3) the velocities under the height of short rods are different, but velocity profile at all locations above the tall rods can appear to converge onto a single logarithmic profile with a slip velocity, which is consistent with the velocity distribution near the water surface of the non-vegetated layer.