The demand for high-precision positioning is increasing in modern marine applications such as marine engineering, marine transportation, marine energy development, and marine monitoring. The improvement of China’s BeiDou Navigation Satellite System (hereinafter referred to as BDS) with the capability of global coverage service has made it possible to achieve high-precision positioning of the ocean using BDS sea-based augmentation technology. In this paper a high-precision positioning terminal deployed on a BDS-equipped buoy is proposed, with emphasis on the composition, key techniques, functions, and performance indicators involved. Multiple experiments have been conducted on the coastal area of the East China Sea in Zhoushan City, Zhejiang Province to test the positioning accuracy of the proposed terminal. The experimental results have demonstrated that the average positioning accuracy based on the BDS sea-based augmentation system can be achieved at centimeter accuracy level, which meets the high-precision positioning requirements of marine users. These results also indicated the promising potential of BDS to provide comprehensive functions and optimal performance.