In this paper, a spherical robot with an internal mechanism for propulsion is briefly introduced. The spherical robot is actuated and steered through a couter-weight pendulum connected to the main axle, a drived motor and a steer motor. A mathematical model of the robot’s dynamic and motion is instructed. The 3D model of the robot is built by SOLIDWORKS and then exported to ADAMS for simulation. For a number of missions, it is shown experimentally that the model agrees well with the results.