In order to solve the problem that mobile robots have strict requirements on operation environment,a light and small spherical land-air amphibious robot is designed,which can be applied to variable and narrow environments.It has two motion modes of rolling on the ground and flying in the air,and it can complete the switching of motion modes autonomously.Firstly,the structure of the robot is designed,including the rolling part,the flight part and the mode-switching part.Based on the Lagrangian method,the kinetic model in different motion modes is established,and the kinematic model based on the Euler equation is established.Finally,according to the motion models of the robot,the attitude controllers in flight mode and in ground-rolling mode are designed,and the comparative simulation experiments of the controllers are conducted.The tests were conducted on a real robot.The experimental results show that the robot can achieve autonomous mode switching and stable motion in different motion modes with controllable attitude,and has certain obstacle-crossing ability in pure ground mode.The structure,the control method and the control strategy switching method are useful for the land-air amphibious deformable robot.