Abstract: In this paper, two-layer rectangular patch with truncated corners structure is applied to design circular polarized units and 64 element high-gain circularly polarized microstrip array antenna at X-band. Antenna substrate uses Taconic-TRF,of which the dielectric constant is 4. 5, the thickness is 0. 81mm and the loss tangent is 0. 0035. Through the actual test, the result show bandwidth(axial ratio AR<6dB)of the 64 element array antenna reaches 500 MHz, array antenna gain is about 21. 2 dB, the relative impedance bandwidth(S11 <-10dB)reaches 6. 9%, the antenna has good circular polarization and impedance matching characteristics. Circularly polarized antenna has a strong anti-jamming capability ,so it can be well applied in the field of electronic reconnaissance, electronic warfare. Circularly polarized microstrip array antenna of this design provides a unit basis for the composition of a larger array and the construction of the phased array antenna.