The invention relates to an underwater repairing system for a concrete face rockfill dam face disengaging area. The underwater repairing system comprises a movable platform, a working bin, a pressuredrainage device, a traction device and a positioning device. The working bin and the positioning device are arranged on the movable platform; the traction device controls the movable platform to moveon the surface of a dam body concrete panel; the positioning device transmits a detection position; the working bin is a pressure bin with an upper closed structure; the working bin is connected witha pressure drainage device; a drilling device and a grouting device are arranged in the working bin; the moving platform moves to the disengaging area, the pressure drainage device is started to drainwater in the working bin, a locally-closed water-free space is formed in the working bin, the drilling device drills a panel at the upper end of the disengaging area, then the grouting device conducts grouting, and repairing is completed. According to the system, the locally closed water-free space is formed in the working bin, and the drilling device and the grouting device are combined, so thatthe underwater economical and efficient repair of the concrete face rockfill dam face disengaging area is completed.