Vegetation is an important part of the ecological channel, and flow structure over vegetation in ecological channel is rather complex. The vegetation resistance to flow is affected by many factors, and there is still no general calculation method to express it. Thus, it is necessary to explore the mechanism of flow resistance over vegetation in open channel. In this paper, the rigid cylindrical sticks arranged in the open channel were used to simulate the stems of non-submerged vegetation in order to investigate the effects of vegetation on the flow. Through theoretical analysis and experimental verification, it shows the form drag caused by vegetation is closely related to the vortex volume created by vegetation. In addition, the total resistance of vegetated channel can be determined by two methods based on vegetation density and flow resistance partitioning, respectively, and both of them are verified by the experimental results. What's more, for rigid vegetation, the drag coefficient is closely related to vegetation density, spacing between vegetation patches and the Reynolds number. The empirical formula among them was established through the experimental results.