In order to solve the problems about the optimal hydraulic section and the internal force ofthe bottom of V-shaped slope wall drainage channel,based on the theories of hydraulics and rigidbar method,the calculating methods for them have been put forward.The results show that the optimalhydraulic section has nothing to do with the depth,and it is more convenient to calculate the internalforce of the bottom of V-shaped slope wall drainage channel by rigid bar method.At last,therigid bar method has been carried out in the case of Pingchuan debris flow to calculate the internalforce of the bottom of V-shaped slope wall drainage channel.