In response to the requirements for gradient observation of the Youjiang River waterway regulation project,the methods of gradient observation are discussed.An implementation plan combining longitudinal gradient and river center gradient is adopted,with a focus on demonstrating the leveling measurement method of river center gradient.By setting an adjustable tubular level on a bamboo raft,a leveling observation method is used to measure the elevation of the river center water surface.Combined with the coordinates and other information measured by GNSS-RTK,the accuracy of river center leveling observation is improved.The results show that the leveling observation method can achieve millimeter level observation accuracy for measuring the river center gradient,which has higher accuracy than using GNSS-RTK.