Abstract: To address issues such as weak stability and insufficient adaptability of wall-climbing robots working on variable curvature wall, a wall-climbing robot of separate structure that the adaptive module is relatively independent from the main body is designed, and its motion performance on walls is studied. Firstly, a mechanical model based on the movement principles of robot on a wall is established. The adsorption forces required for longitudinal/lateral direction switching, wall-climbing movement, and obstacle crossing without slipping or overturning are calculated. Additionally, the changes in the robot body posture during longitudinal and lateral movements on circumferential and radial curved surfaces are analyzed. Subsequently, the magnetic circuit design and parametric simulation of the permanent magnet device are performed to analyze the effects of air gap distance and wall thickness on the adsorption force. The adsorption forces of the robot on different curved surfaces and in various motion modes are simulated to optimize the design of the permanent magnet. Finally, experimental validation is performed to assess the climbing performance and adaptability of the climbing robot on variable curvature surfaces. The results show that the designed wall-climbing robot features flexible longitudinal/lateral switching movement, stable adsorption, and strong adaptability to variable curvature surfaces, with a minimum curvature adaptability of 0.46 m and the capability to carry 7.2 kg equipment on a 90° wall.