The Outdoor Mobile Robot plays an important part in outdoor science exploration, community monitor and so on, and is becoming a research hotspot. On the basis of the outdoor mobile robot with diameter-variable wheels, this paper builds a motion control system which could control the movement of the outdoor mobile robot with diameter-variable wheels and creates an adaptive control model which could open and fold the wheel automatically according to the road condition. Then the mobile robot could run on the rough terrain and keep steadily on the mass centre margin. A series of simulation has been done for the adaptive control model, and the simulation results demonstrate that the adaptive control model is feasible.