With the development of micro-robot technology, its characteristics such as strong controllability and flexible action have been widely concerned by researchers at home and abroad. In the field of biomedicine such as targeted drug delivery, micro-robots have a good application prospect. Especially in conquering major diseases such as cancer, the emergence of micro-robots will undoubtedly bring good news to the majority of cancer patients. In the past research of micro-robots, the motion characteristics of rigid robots are mostly concentrated in ideal environment, and the motion mechanism of rigid robots on complex walls has not been systematically studied. In this paper, fluid–structure coupling simulation was carried out based on COMSOL Multiphysics. For a rigid robot driven by magnetic control chemistry, the influences of the robot’s shape, size, surface sliding velocity and height from the wall on the motion velocity under smooth wall conditions were first explored. Then, according to the existing simulation results, two kinds of robots with the highest and lowest motion efficiency are selected to study their motion performance near complex walls, covering the key performance indicators such as motion speed and deflection angle. The simulation results show that the motion efficiency of the robot is the highest when the head shape is sinusoidal and the surface sliding speed is constant. At the same time, the critical magnetic moment to satisfy the good motion stationarity of the micro-robot should be greater than or equal to 1 μN·μm.