A microstrip antenna array is designed based on the theory of cavity and mode of rectangular patch. The array is constructed on the Rogers(5880) as dielectric substrate material；and operating center frequency is 24 GHz. Research is conducted by using electromagnetic simulation software, such as A Dissertation Submitted(ADS)，High Frequency Structure Simulator(HFSS), as well as Matrix Laboratory(MATLAB) programming. According to the requirements of antenna’s impedance match and gain, a power divider network is also designed. Finally，the microstrip antenna array with 6×14 units is simulated by using the HFSS software, some core parameters of the array including in gain, bandwidth, voltage standing wave ratio, and emission patterns，are obtained. Fabricated sample is tested in the platform of microwave dark room of Institute of Electronic Engineering in China Academy of Engineering Physics. Results are in very good agreement with requirements.