Abstract: To investigate the along-range variation characteristics of flow velocity and longitudinal dispersion coefficients of water flow in open channels under the influence of floating vegetation, in this paper, a three-dimensional numerical simulation was carried out by the k-εmodel in Fluent software, and compared with the results of flume tests. On the basis of reasonable model validation, the vertical distribution characteristics of longitudinal time-averaged flow velocity of water with different depths of root into water and coverage rates of floating vegetation were investigated. The enhanced N-zone model served as the basis for the analysis of the longitudinal dispersion coefficient. The results showed that the vertical structure of floating vegetated flow could be divided into vegetated flow layer, non-vegetated flow layer and near-riverbed layer. The depth of the vegetation root into the water and the covering rate were connected to the maximum longitudinal velocity, which was found in the non-vegetated flow layer. While the longitudinal velocity in the near-riverbed layer and non-vegetated flow layer increased with increasing coverage rate and depth of vegetation root into water, the longitudinal velocity in the vegetated flow layer decreased with increasing coverage rate and depth of vegetation root into water. The greater the vegetation coverage rate and the depth of root into water, the greater the velocity difference between the vegetated flow layer and the non-vegetated flow layer. The longitudinal dispersion coefficient showed a tendency of first increasing and then decreasing along the streamflow direction, with the sharpest dispersion in the middle and lower reaches of the vegetation zone, and was positively correlated with the depth of vegetation root into water and coverage rate.