Abstract: A series of overland flow experiments are conducted, focusing on the effects of the different height flexible vegetation on the hydraulic characteristics of the overland flow. Experimental results show that the 4 cm vegetation shows the best effect on the overland flow while the 15 cm vegetation shows the least effect. The difference of the effects reduces with the increase of the slope. With the same coverage rate, the flow resistance increases and then decreases with the increase of the Reynold's number. That is because the main flow resistance is the bed resistance in case of a small Reynold's number while the vegetation resistance prevails in case of a large Reynold's number. Besides, the revised coefficient ranges from 0.2 to 0.4 on smooth slopes while 0.4 to 0.8 on vegetation slopes, and the revised coefficient increases with the increase of the averaged velocity.