Abstract: In deep space TT&C mission,the space time delay and Earth rotation make the narrow beam of large ground antennas unable to cover the corresponding orbit area,which leads to the quality deterioration or even interruption of the communication link. A technique for a real-time beam separation correction scheme for deep space uplink and downlink communications is presented,which provides a close relationship between the beam squint angles and the corresponding feed displacement for a reflector antenna with a beam waveguide(BWG)or multiple reflector system. The simulation results of 35-meter antenna at Ka band(34 GHz)show that the uplink beam gain loss is less than 4.25 dB by moving the uplink feed position when the up/downlink beam separation angle is 0.032 72°. It is also useful to determine the feed offset position to correct the beam deviation caused by the imperfect antenna mechanical structure and the mirror misalignments of the complex multiple reflector system.