Abstract: The GNSS nulling antenna array with multiple antenna cells is usually used to form the beam null in the direction of jamming with large power. This is an effective anti-jamming method. Here the 2D short baselines in a nulling antenna array are utilized. According to direction finding principle of multi-baselines interferometer in electronic reconnaissance, the measurement result of short baseline is naturally used to solve the phase difference ambiguity of long baseline for GNSS attitude instrument. In this way the integer cycle ambiguity from GNSS attitude instrument is removed in real time. In this method GNSS attitude instrument is combined with nulling antenna array. It enhanced not only the speed for ambiguity removing, but also the anti-jamming and anti-deception ability of the whole system. It is an important reference for the application development of GNSS attitude instrument and nulling antenna array.