The project addresses the issue of seepage in the transverse joint of the dam at Jinghong Power Plant through a comprehensive 50-day treatment plan. The project is divided into five critical phases: construction preparation, underwater inspection, treatment of the upstream face of the transverse joint, drilling and grouting within the gallery, and final acceptance and equipment organization. The construction site is located upstream of the dam, with the on-site project team and personnel accommodations arranged in nearby houses to ensure convenience and safety for the workers. Overwater operations will be conducted from a 10*10 m construction platform, which is movable and positioned by ropes fixed to the dam, facilitating rapid deployment of personnel and equipment. The underwater work platform is constructed from 10# channel steel with rollers for flexible movement on the dam surface. The detailed construction process for treating the seepage in the transverse joint includes meticulous planning from the preparation phase, through underwater re-inspection and crack marking, opening a “U” shaped groove, drilling grouting holes, sealing the joint surface, conducting air pressure tests, grouting, removing grouting pipes, installing SR waterproof modules, and finally, underwater camera inspection for acceptance, ensuring each step meets the expected technical standards. Drilling and grouting operations within the gallery follow a sequence from low to high and from upstream to downstream to ensure the continuity and integrity of the grouting effect.