Abstract: A broadband circularly polarized beam-switched microstrip antenna easy to be controlled and realized has been proposed based on "Satcom on the Move" for maritime satellite communication application. The impedance bandwidth and circular polarization bandwidth of the antenna element have been broadened by using four probe phase serial rotated feed network design with the miniaturization technology. And the antenna gain has been enhanced by using an antenna array. The Wilkinson power divider and PIN diode switch phase shifter are used to control power distribution and phase difference. A broadband multi－beam forming network has been realized through the capacitor compensation technology to improve the microstrip switch circuit matching. The final three beam-switched two element antenna array for maritime satellite communication has been made and tested. The measured results show that the VSWR of the proposed antenna is lower than 1. 5 during the whole INMARSAT work band. The antenna can achieve -20 degrees to 20 degrees of space beam coverage with gain of 9dB and good circular polari－zation performance. It verifies the validity of the design scheme.