During the Baimaosha regulatory engineering in phase I of the 12.5 m deepwater channel of the Yangtze River below Nanjing city,solutions are found to counter the operation difficulties of big stage difference between the ebb tide and flood tide,complex dynamic flow conditions and great inspection difficulty for the underwater soft mattress installing quality.Implementing the inspection program including buoy’s down-hanging,underwater detection,side scan sonar and ultra-short baseline methods,we can control the soft mattress installing quality and meet the project needs