Abstract: The case study was conducted on the project about Hejiang Depot Access Tunnel built by large diameter shield undercrossing Dongfeng River with little distance and ultra-shallow cover for Chengdu Metro Line 18, the comprehensive measures of replacing silt with clay at the bottom, constructing waterproof layer and anti-floating plate, controlling driving parameters of shield, and conditioning ground and grouting behind the segment for the second time were put forward. The safety hazards of construction undercrossing the river were effectively solved, the anti-floating capacity of segment structure of shield tunnel was improved and good social and economic benefits were generated. The safe construction technology of large diameter shield undercrossing river with little distance and ultra-shallow cover was established to provide technical references for similar projects in the future.