In view of the problems of low efficiency and difficult deformation control in the construction of large-area sand filling near the existing bridge structure，combined with the east artificial island project of Shenzhen-Zhongshan Link，this paper determines the sequence and method of filling under the bridge based on numerical simulation，explains the key construction techniques of backfilling island construction，and verifies the construction effect by monitoring data and arch silt sweeping.The results show that the backfilling principle of “pile-sand quilt-cross-bridge left/right alternating”，combined with sand splitter and other devices can control the deformation of the existing bridge within ±5 mm and reduce 66.7% of arch siltation.The deformation correction effect of pile back pressure and unloading in the opposite direction is significant.The backfill sand volume needs to focus on the backfill density，mud content，and the loss of the filter layer of the island wall.The backfill sand loss rate in the test section of this project is 4.21%.