A broadband circularly polarized antenna with C-band single-fed parasitic array is designed in this paper. The antenna adopts the adjacent double-layer F4B dielectric substrate, and the circular polarization is realized by slotting on the square drive patch and adopting the design of parasitic array. The design steps of the antenna structure are described, and the effects of each structure on the antenna impedance bandwidth and axial ratio bandwidth are studied. The effects of the parasitic patch tangent length and the slot width in the drive patch on the axial ratio and bandwidth of the antenna are also investigated. The circular polarization pattern of the antenna is simulated. The simulated results show that the antenna has a right-hand circular polarization is achieved at 5.5 GHz with a maximum gain of 8.1 dBi. The broadband circularly polarized antenna was fabricated and tested, and the test results were basically consistent with the simulation results. The measured impedance bandwidth of the antenna was 1.3 GHz, and the axial ratio bandwidth was 1.26 GHz. The designed stacked antenna has the advantages of compact structure, simple assembly and large axial ratio bandwidth.