The C-shaped sealing plate in the butt sealing device of the Three Gorges ship lift is prone to fractures，and its sealing maintenance is inconvenient. Hence，this study builds the mechanical models of the C-shaped sealing plate and connecting bolts in different operating conditions. The analysis of the bolt strength check shows that the tensile stress on the connecting bolts of the C-shaped sealing plate is greater than the tensile stress limit of the material in the process of discharging interstitial water. According to the analysis results and the structural characteristics of the field equipment，we design the reinforcement tooling of the C-shaped sealing plate，and the installation and application verify that the stress on the bolt can meet the design requirements. Meanwhile，we design a C-shaped sealing maintenance platform to satisfy the requirements of rapid maintenance and replacement，which solves practical engineering problems.