A tidal sluice was built in 2015，and left lateral seepage of was found during test run，with filling collapse at the backside of retaining wall，vortex phenomenon at 10m from left side of upstream retaining wall，uplifting at middle apron next to downstream stilling basin，and emitting with water column.The lateral seepage danger was controlled with emergency rescue，and defectiveness detecting verified by geological radar.It is indicated that the emergency rescue was effective and appropriate，defectiveness detecting with geological radar provided technical support，and ensured the safety operation for the project.