The invention discloses a method for synchronous transmission of digital array antenna baseband excitation data. The method is featured by small channel phase error, simple processing of digital processing part and low power consumption baseband excitation data. In the method, optical fiber is adopted as a long-distance transmission media between a collecting end and a receiving end, 1-N ADC1-ADCNof the collecting end perform data sampling on RF signals, and convert the signal into an intermediate frequency signal, packages data according to a JESD204B protocol and converts the data into a high-speed serial data flow, and sends the data flow to an electro-optical conversion module to be converted into optical signal, then an optical fiber photoelectric conversion module recovers the optical signal into an electric signal and sends the electric signal to the receiving end FPGA1-FPGAK to complete data recovery, then data is aligned through channel calibration, sample signals with data aligned are simultaneously transmitted to a received data processing end FPGA, and a full link data synchronous transmission homologous synchronous clock network synchronizes data.