A new circular polarization (CP) broadband microstrip antenna with annular slot in the patch is designed in this paper, which is fed by the L-probe with its phase difference is 90°. Through slotting in the annular patch, the axial ratio and impedance bandwidth are effective increased. The bandwidth of traditional circular polarization is limited by the common bandwidth of impedance, axial ratio and gain. The relative bandwidth of proposed antenna is up to over 53%, with its effective bandwidth is 1.1GHz to 1.9GHz. The frequency band covers four navigation systems of GPS, GALILEO, COMPASS and GLONASS. The proposed antenna can be easily debugged with low cost and widely used in Global Satellite Navigation System.