A new spherical mobile robot BHQ-1 is designed. The spherical robot is driven by two intally mounted motors that induce the ball to move straight and t around on a flat surface. A dynamic model of the robot is developed with Lagrange method and factors affecting the driving torque of two motors are analyzed. The relationship between the ting radius of the robot and the length of two links is discussed in order to optimize its mechanism design. Simulation and experimental results demonstrate the good controllability and motion performance of BHQ-1.