The researches on two-wheeled self-balancing robots have gained momentum in recent decade around the world. This paper describes the kinematics model of a two-wheeled self-balancing autonomous mobile robot. After mechatronics system design of the robot is completed, the analysis of the whole kinematics model can be divided into two wheels and a body. Then the velocity decompositions of robot wheel and body are analyzed respectively. After the left and right wheel kinematic model is established based on above velocity decomposition method, and the kinematic model of self-balancing robot's body is also calculated by this method. The whole kinematics model of the two-wheeled self-balancing robot system is then established. The effectiveness of the kinematics model is testified by the simulation analysis on ADAMS and experimental validation.