Abstract: The view-angle requirements for an on-board Earth-surface vehicle's antenna, that keeps data communications between the vehicle and a known GEO satellite were analyzed,taking into account of the vehicle movements in both geographical locations(in longitude and latitude) and attitudes(in pitch,yaw and roll) within a given range.The guidance for the on board antenna was given as well.By this way,the view-angle and polarization performance of the antenna for keeping continuously communications with the satellite was defined,and any over designed performance coursing unnecessary engineering efforts can be avoided.