Abstract: The ship's wall-climbing robot for removing paint is adsorbed on the wall of the ship's steel plate by a permanent magnetic adsorption device. Aiming at the design requirements of reliable adsorption and flexible walking of the wall-climbing robot, a permanent magnet adsorption device based on Halbach array is designed in this paper. The mechanical model of the wall-climbing robot is established to obtain the adsorption force required for reliable adsorption. Taking the ratio of adsorption force to mass of the permanent magnet as the objective function, the structural parameters of the permanent magnet are optimized, and thus the magnetic energy utilization rate of the permanent magnet is greatly improved. Through the walking experiment of the wall-climbing robot, it is verified that the ship's paint removal wall-climbing robot meets the design requirements of reliable adsorption and flexible walking. The research results obtained in the optimized design of permanent magnet adsorption device have remarkable significance in promoting the progress of ship's wall-climbing robot for removing paint technology and improving the social and economic benefits.