Abstract: In order to improve the performance of antenna array beam-pattern, this paper proposes a method of signal steering expansion based on conjugate virtual array. Conjugated virtual array elements are used to expand the array and the array aperture is increased without changing the actual number of array elements. The side-lobe level is reduced while the manufacturing cost of the antenna is not increased. The signal steering vector is extended on the basis of the virtual array to make the array beam-forming effect more robust. In the case of amplitude and phase errors existing, 11 array antennas are simulated with and without the interference. The effectiveness of the above method is verified by comparing the simulation results of the original array beam-pattern, the virtual array beam-pattern and the beam-pattern after expanding the steering vector.