Abstract: In order to simplify the procedure of designing circular polarization foursquare microstrip antenna unit, a novel circular polarization foursquare microstrip antenna unit with cutting corners and slots has been proposed. By making rectangular slots on the microstrip antenna unit, the repeating iterative process in the process of adjusting the resonance frequency and axial ratio of the circular polarization antenna has been avoided and the adjusting time has been shortened. The influence of different width and depth of the rectangular slots on the antenna to the impedance and axial ratio has been analyzed and a microstrip antenna unit with good performance has been designed by simulation. The final simulated relative impedance bandwidth (S11 <-10 dB) of the single layer microstrip antenna is 2.05% (1.980 ~2.021 GHz) and the final simulated relative axial ratio bandwidth (AR<3 dB) is 0.50% (1.995 ~ 2.005 GHz). The antenna unit has been fabricated and tested. The tested relative impedance bandwidth (S11 <-10 dB) and relative axial ratio bandwidth (AR <3 dB) are 2.05% (1.975 ~2.016 GHz) and 0.50% (1.990 ~2.000 GHz) respectively. The tested results agree with the simulated results very well and confirm the validity of this design.