A large number of phytoplankton such as algae will adhere to the bottom of the fish tank and around the tank wall, which will lead to water pollution and frequent fish disease. In order to solve the problem of manual cleaning, an intelligent underwater fish tank cleaning robot based on crawler walking and disc brush cleaning was studied. The overall system of the cleaning robot was designed, including the overall structure of the robot, the motion system, the cleaning system and part of the control system. At the same time, the mechanical model and hydrodynamic analysis of the cleaning robot were established to provide good motion stability, structural stability and hydrodynamic characteristics in the process of cleaning. Model prototypes were made as required and underwater cleaning tests were simulated. Through the analysis of the prototype test, the results show that the main factor affecting the cleaning performance is the brush speed when the brush diameter, the brush material, the grounding pressure and the cleaning path are not considered, and the optimal combination scheme is that the brush speed is 600 r/min and the drive speed is 0.4 m/s.