The present invention discloses a data transmission method. The method includes: receiving, by a data processing apparatus, at least two data flows transmitted from at least two remote base stations among multiple remote base stations, aggregating the at least two data flows into one flow of output data, and transmitting the output data to a central site device; or receiving, by the data processing apparatus, one flow of synthetic input data transmitted from the central site device, restoring the synthetic input data to at least two data flows before synthesis, and transmitting the restored at least two data flows to corresponding remote base stations.