Abstract: The theory of circularly polarized microstrip antenna is analyzed. A double structure with electromagnetic coupling feed is proposed to replace the traditional feed structure. By optimizing the L microstrip feed shape, the distance between feeder and radiation unit and the feeder impedance matching, a circularity polarized antenna prototype with wide angle axial ratio is manufactured. The gain, axial ratio and voltage standing wave ratio(VSWR) of the prototype are tested, and the results achieve the predicted goal.