Abstract: There are some mistakes in the state eqution derived by the dynamic equation by omitting many coupling factors for the sake of simpleness, which is not consistent with the practice, since the system is not controllable. Based on the dynamic equation, and combined with the practice, this paper gives out the modified state equation, making sure that it is controlable. A LQR controller is designed to stabilize the single-wheel robot (SWR) and to make it yaw. To test the robustness of the system, twostep disturbances were applied on the lateral and longitudinal direction, respectively. Both the simulation and the experiment results verify the modified state equation, which lays the fundation for further advanced control algrothim to be performed on the SWR.