In order to solve the safety risk problem of underwater human leveling caused by low tide level, high flow rate, and complex construction conditions at the top of E1 pipe section at the joint of the west artificial island of ShenzhenZhongshan link, automatic positioning measurement and control system of excavator equipped with GPS is developed to leveling caisson gravel foundation bed of load reduction. The position and attitude of the cab are calculated by GPS and biaxial inclinometer, and then the position and attitude of each swing arm and bucket can be calculated by the uniaxial inclinometer on each swing arm to guide the driver to carry out the construction leveling of the foundation bed. After the leveling of the gravel subgrade bed, the maximum value of elevation acceptance is +4.2 cm and the minimum value is -3.5 cm, meeting the design and construction requirements and improving the leveling accuracy of the gravel subgrade bed.