An automatic leveling system based on three degrees of freedom hydraulic boom of excavator was designed to meet the leveling requirements of underwater riprap foundation.The mechanical structure of the boom was reformed,and the working load was calculated by experiments,and the reliability of the modified structure was verified by finite element method.The forward and inverse kinematics models of the boom were built based on D-H method and geometric method,and the trajectory motion of the shovel tip was transformed into the cooperative control of the boom components.The electro-hydraulic proportional position control system of the boom was designed based on PID control,and the feasibility of the drive control system of the boom was verified by AMESim.Combined with Beidou positioning technology,the framework of the automatic leveling system of the boom was built,and the positioning and leveling process suitable for engineering application scenarios was proposed.Finally,the automatic leveling system was verified by engineering test and application.The test and application results show that the leveling efficiency and cost of the three degrees of freedom hydraulic manipulator are higher,and the leveling accuracy also meets the construction requirements.