Aiming at the problem that the bandwidth of traditional circularly polarized microstrip antenna is narrow, a new type of ultra-wideband circularly polarized printed antenna is proposed. The antenna structure is simple and only consists of C-shaped radiation patch and an improved ground plane. With microstrip feed mode, the size of the entire antenna is only 25 mm×25 mm×1 mm. By optimizing the C-shaped patch and adding triangle and small rectangular perturbation structures on the ground plane, the impedance bandwidth and axial ratio bandwidth of the antenna can be effectively increased. The design process of the antenna is given, and the working mechanism of the circularly polarized antenna is analyzed from the surface current distribution. Besides, the antenna is fabricated and measured. Simulation and measurement results show that the antenna has ultra wide impedance bandwidth and axial ratio bandwidth. The working frequency band of the antenna is 4.4-11.6 GHz (the relative bandwidth of 90%), and the 3 dB axis ratio bandwidth is 3.6-11.3 GHz (the relative bandwidth of 103.4%). The radiation performance and gain characteristics of the antenna are measured and the measured results are in good agreement with the simulated results, which proves the effectiveness of the antenna. The antenna can be applied to ultrawideband wireless communication systems and satellite communication systems.