This paper introduces the design method of a dual band microstrip patch antenna, from the most basic of microstrip patch method using bilateral radiation, a dual band microstrip antenna is designed, simulated using HFSS software, results show that, choose a 50 ohm coaxial cable feed position to make the antenna work at the center frequency respectively in 9.96GHz 12.84GHz. And in the 9.96GHz and 12.84GHz echo loss to minimum, bandwidths are respectively 270MHz and 550MHz, antenna has good dual-band resonance characteristics.