Abstract: Aims at the data of sea clutter received by high frequency(HF) ground wave radar will be masked by sea clutter when the ship target located the site of Bragg peak, the character of space-time coupling of sea clutter is analysed, and space-time adaptive processing (STAP) is applied to over the horizon radar, a method is proposed to eliminate mask effect caused by the spectrum of sea clutter. Simulation results in real data show that the algorithm for suppressing sea clutter is efficient and practical.