In order to manufacture antenna integrated with RF-MEMS switch on the same substrate, a silicon wafer was used as substrate. As the high dielectric constant of silicon (ϵr=11.9) degrades an antenna efficiency and excites surface waves especially at high frequency, removing substrate under the antenna and giving birth to an air cavity is a general way to reduce the dielectric constant of silicon. In this paper, a planar array antenna of 2 elements is designed according to the research of K band antenna of air communication equipments based on MEMS technology, and its performance meets the demands, which provides an effective method for designing and manufacturing of Ku band and X band antenna. The microstrip array antenna is designed with the element and simulated in HFSS. The simulation result matches well with the demand.