Using Lagrange equation and other mechanics methods,this paper analyzes the motion characteristics of rolling and turning of a micro-spherical robot,and achieves the conditions of jumping.A general dynamics model is built based on the analysis of characteristics of precession,which can make the robot roll along any curve.A virtual prototype of the spherical robot is developed,and the motion simulation is conducted.The result verifies the correctness of above analysis.The work in this paper establishes the foundation for further research on nonlinear control of spherical robot.