The invention relates to a multi-channel synchronization up-conversion system and method based on a transmitting antenna. The system comprises a data high-speed transmitting unit, a synchronization clock unit, a multiplexing data frame synchronization processing unit, a data unpacking unit, a data phase synchronization adjusting unit, a multi-channel digital up-conversion unit, a transmitter and the transmitting antenna. The multi-channel synchronization up-conversion method provided by the invention comprises the steps of: converting received serial data into parallel data through frame synchronization processing and data unpacking; conducting phase synchronization adjustment on the parallel data under the control of a synchronization clock; removing the frequency spectrum of signals in a full digital mode on the basis of finishing frame synchronization and phase synchronization; and finally, transmitting radio frequency signals through the transmitter by an antenna feedback source. In the invention, multi-channel synchronization up-conversion can be accurately realized in the presence of disturbance and delay in communication channels; the synchronization problem of the multiplexing coherent transmission of the transmitting antenna is solved; and the reliability and the stability of communication among all transmitting channels of the system is ensured.