Abstract: The conventional anti-seepage treatment of cofferdam is the construction of high-pressure rotary jet grouting with three pipes.Because the high-pressure water jet is used as the main jet,the slurry becomes thinner and loses faster in the flowing water-rich stratum,so the effective waterproof curtain wall cannot be formed.The average drop of water head inside and outside Tangjiadu hydropower and navigation project foundation pit is 11 meters,and the maximum is 23 meters.The conventional high-pressure rotary jet grouting cannot meet the complex construction conditions such as dynamic water and high head difference.Through the transformation of conventional high-pressure rotary jet grouting equipment,the original high pressure water,medium pressure air and low pressure slurry conventional three pipe medium adjustment into high pressure cement slurry,compressed air,sodium silicate slurry new three-pipes medium sent to the bottom of the hole mixed into the wall.The technical parameters of the new three-pipe high-pressure rotary jet grouting construction were determined by setting experimental holes for grouting.The construction of cofferdam with new three-pipes high-pressure rotary jet grouting has ensured the construction quality,reduced the cost,and speeded up the construction progress.