Abstract: Based on the requirement of automatically getting on wall and cushioning, the form mechanism of pull force of robot, cause and process of touch wall were analyzed. Utilized the principle of aerodynamics, calculating method of the pulling force was given and the result was verified through experiment on the robot physical prototype. The robot closes to the wall under the effect of pulling force and collides at the same time. In the colliding process, cushion device which is composed of skirt edge and support mechanism undertakes absorption of impulsive energy. The former also guarantees sealing after the robot closing to the wall, its rigidity cannot become too strong. The later also guarantees that the robot walks steadily on the wall, so its rigidity cannot become too weak. The method of defining cushion rigidity was proposed. The criterions of assigning cushion rigidity to skirt edge and the support mechanism were given. This method could be used to engineering analysis of wall-suspension robot.