Small and medium-sized pipelines, especially thermal pipelines, are difficult to carry out on-line quality inspection. In order to solve this problem, according to the required environmental requirements, a permanent magnet adsorption bihemisphere type motion carrier was designed for the quality and thickness of steel plate. By analyzing the forces on different surfaces and planes, the dynamic and kinematic models and design control rates were established. Lyapunov direct method was used to verify the walking stability of the mechanism. The physical prototype was designed, and the experiments were carried out on different surfaces and surfaces. The experimental results and simulation results are almost the same, which verifies the feasibility and practicability of the dual-drive permanent magnet motion carrier