The invention discloses a large shipborne radar stable tracking device. The large shipborne radar stable tracking device comprises a fixed base, a driving branch, an upper platform, an azimuth drivingmechanism and a pitch driving mechanism. The upper platform realizes two rotational degrees of freedom and one movement degree of freedom through the movement of the driving branch, and roll, pitch and heave motion of a ship can be compensated, so that the upper platform plane remains stable; and an azimuth rotary table can drive a pitch seat to perform azimuth rotation, the pitch seat drives a radar antenna to perform the pitching rotation, and the adjustment of the azimuth angle and pitch angle of the radar antenna on the pitch seat is realized. The five-axis form isolates the impact of ship shaking on a tracking radar and improves the tracking accuracy of the radar antenna. A protruding rod of the device is guided by a columnar cylinder in the fixed base, the overall rigidity and carrying capacity of the mechanism are improved, the size is small, floor space is small, and arrangement is convenient.