Abstract: This paper proposed a single wheel robot (SWR) applying flywheel to maintain lateral balance, and derived the dynamic model on the lateral direction according to Lagrange equation.Based on the dynamic model, PD and LQR controllers were designed, and performed in simulation and physical prototype, respectively.During the experiments, the SWR initially leaned to the side direction at a certain degree, and then it finally stabilized at the vertical stable position by controlling the flywheel motion, completing the lateral stabilization of SWR.Both results verified the dynamic model.