Abstract: The vertical velocity distributions in the vegetated channel and the relationship between resistance coefficient and flow depth were measured in laboratory experiments.Based on the assumption that the velocity in the region with vegetation keeps constant,the velocity distributions above the top of vegetation may be well predicted which closely fit the results of the experiment.And then the relationship between the resistane coefficient and flow depth for the vegetations under the unsubmerged and submerged conditions is deduced theoretically.Finally an example is given that the relationship between n and h for reeds is extended successfully from unsubmerged to submerged condition,and some experimental results approve such a conversion.