This paper presents an amphibious spherical robot with water surface posture stability. The robot is equipped with two sets of propulsion systems: an internal pendulum and a pair of main-secondary motors for rolling motion, and external left and right propellers for water surface propulsion motion. To enable autonomous motion of the water surface spherical robot, a path planning framework is designed, and linear and angular velocity controllers are developed based on the PID control algorithm. Additionally, by controlling the main-secondary motors, the robot exhibits both stranding resistance and self-stabilization posture capability. The experiments confirm that the robot autonomously follows predefined paths with accurate linear and angular velocity control and exhibit satisfactory self-stabilization ability on the water surface.