Aiming at the technical difficulties such as high retaining wall of expanded lock near the original first-line lock building,strict deformation requirements,complex construction conditions,and building lock cofferdam during the construction period,through comparison and selection,the form of double row piles structure with chest wall was proposed,and its mechanical characteristics were analyzed by finite element method.The monitoring results show that compared with the traditional structure,the stress and deformation of the pile body of the structure are relatively small,which can guarantee the safety of the existing buildings nearby,and has the popularization value in projects with similar boundary conditions.