Abstract: In order to improve 3 dB axial ratio beamwidth (ARBW) of the microstrip antenna, a miniaturized wide 3 dB ARBW circularly polarized microstrip antenna is proposed, and it is designed by using the structure of bilayer dielectric substrates and the methods of grooving on radiation patches, feeding by single point coaxial probe and perturbing by truncated corners. The size of the antenna is 0.40800.40800.0360 at central wavelength (0), and the operating frequency covers IEEE 802.16e (3.5 GHz) frequency band. Using the simulation software (Ansoft HFSS15.0) based on finite element method to optimize and simulate the antenna, the design results show that 3 dB ARBW is 230~255, the band of voltage standing-wave ratio (VSWR) less than 2 is 290 MHz, the peak gain is 4.11 dB at 3.5 GHz. Also, the test results are in good agreement with the simulation results. So ARBW of antenna can be broadened by the proposed structure and method effectively.