Abstract: Deep-sea cage aquaculture is an important marine aquaculture mode. Regular cleaning of cage nets is a critical step to ensure aquaculture quality and safety. Currently, nets are commonly cleaned manually, which is time-consuming and labor-intensive. As deep-sea cages grow larger, their manual cleaning become more difficult. Net washing robots provide a safer and more convenient way to clean nets for deep-sea cages. However, it is challenging to design controllers with strong disturbance resistance and low energy consumption for net washing robots, as the forces are difficult to model and the states are hard to observe during net cleaning and underwater shuttling. Moreover, conducting comprehensive experiments and data recording requires high costs and much time. To address these problems, we constructed a simulation system for a net washing robot based on the physical simulation environment Gazebo, considering the presence of thrusters and washing discs. Besides, we analyzed the effects of various hydrodynamic characteristics in underwater environment, such as added mass and damping, and factors like flow field environment on the washing robot. The established net washing robot can obtain complete data on the underwater operation of the net washing robot, verify control performance, and compare model performance more easily, thereby assisting in the controller development of washing robots.