Abstract: The paper has briefly analyzed the construction new techniques and result of the TGP stageⅡ cofferdam safety monitoring, through analysis we consider that 1.0 m wide impervious wall, which is made by the pulling out the tube bore method, hydraulic auto-balancing strain gauge, and embedding the earth pressure gauge and the osmometer by using hanging the cloth method, is workable. The maximum deformation of waterproof wall is 612.32 mm, less than design value of 674 mm ; the maximum tensile stress and compressive stress are 0.094 MPa and -1.392 MPa respectively, which are within the range of allowable material strength. The upstream impervious wall and the downstream one reduce water head to 51.58 m and 51.04 m respectively. The effect of the impervious walls is remarkable, and the seepage discharge is between 26～62 L/s, which is 600 L/s less than design value. So it is concluded that the waterproof wall works in normal condition.?