Abstract: A novel non-smooth controller of the second order control system with a disturbance was proposed to control the attitude of a small floating satellite antenna in sea. Aiming at the standard second order integral system with a bounded disturbance,a novel non-smooth controller with a better rapidity,stability and strong disturbance rejection was studied. Several works were carried out including the stability proving,the strong disturbance rejection validating,sea disturbance properties analyzing,the models developing,and the disturbance rejection ability analyzing with different disturbances. Finally,a non-smooth PID azimuth controller of a small floating antenna was constructed based on the novel non-smooth controller to control the antenna's azimuth. Simulation and part experiment results validate that,the non-smooth PID controller of the small floating satellite antenna can quickly and steadily control the antenna's azimuth,and well reject the disturbances in sea to ensure a communication quality between the antenna and the target satellite.