Inchworm-type wheeled mobile robot is a non-comprehensive, all-driven system. This paper establishes a kinematical model for such system. Based on the kinematical model, the motion of the system is analytically studied, and the simulation of the motion for this system is conducted with the means of Pro/E. The system in the dynamic motion presented make the collision avoidance and path seeking easier. It also provides a motion mould for the simulation, and proves the theoretical analysis is right.