The invention relates to an aquaculture cage underwater cleaning device. The aquaculture cage underwater cleaning device comprises a rotation shaft provided with a center blind hole, a shaft sleeve and a cleaning disc. The rotation shaft is provided with at least one water inlet communicating with the center blind hole in the radial direction. The shaft sleeve is fixedly arranged at the outer portion of the rotation shaft. The position, corresponding to the water inlet, of the inner wall of the shaft sleeve is provided with a circle of ring groove, the side wall of the shaft sleeve is providedwith a water inlet hole communicating with the ring groove, and the water inlet hole is connected with an immersible pump. A plurality of branch pipes are evenly arranged on the cleaning disc, and the tail ends of the branch pipes are connected with nozzles. The horizontal included angle is formed between the water outlet direction of the nozzles and the end face of the cleaning disc, and water sprayed to the cage generates the rotation reverse acting force on the cleaning disc. The aquaculture cage underwater cleaning device is simple in structure and convenient to operate, the cage aquaculture environment is guaranteed, and the aquaculture variety quality is improved; and the nozzles are obliquely arranged, the reverse acting force of the sprayed water flow is utilized for driving the cleaning disc to rotate, design is ingenious, the cleaning effect is good, the cleaning efficiency is high, and the automation degree is high.