Abstract: A novel aperture-coupled circularly polarized microstrip antenna is proposed, which is used in rectenna system. The aperture-coupled single-feed antenna could be integrated and matched to the circuit of rectenna easily. An electromagnetic simulator is applied to analyze the circularly polarized microstrip antenna. An element has been designed and manufactured. The measured results are in good agreement with the simulated results. The antenna has good circular characters at 10.25GHz. The experimental results show that the axial ratio is 0.3dB at the centre frequency, the 3dB bandwidth reaches 160MHz, and the bandwidth of VSWR below 2 reaches 800MHz.