A downstream bandwidth transmission method for a passive optical network includes: an optical line terminal (OLT) sends downstream bandwidth allocation information in a downstream frame to a plurality of optical network units (ONUs); where the downstream bandwidth allocation information comprises a plurality of downstream bandwidth entries for the plurality of ONUs, each downstream bandwidth entry in the downstream bandwidth allocation information comprises ONU indication information for a respective ONU and downstream bandwidth feature information for the respective ONU, such that each of the plurality of ONUs receives respective traffic data within a downstream bandwidth allocated to the respective ONU.