A two-dimension scanning of phased array antenna has been presented. Aperture coupled microstrip patch antenna (ACMPA) elements are used to form a 2×2 array operating at 20GHz. The array is monolithically fabricated with RF MEMS switches by using surface micromachining and anodic bonding process. The main beam can steer in two dimensions when the phase shifters are on the different state. The measurement results show that the array can complete a beam steering angle of approximate ±30° in both E-plane and H-plane, and the highest gain is 9.5dB.