Abstract: Embodiments of the present invention provide a communications method, a communications system, an access network device, a terminal, and a core network device. For all UEs accessing the access network device, before relay node selection is performed, it is determined which UEs are capable of serving as candidate relay nodes, so as to perform a relay node selection operation only on the UEs that are capable of serving as candidate relay nodes when performing the relay node selection, thereby saving operation overhead, reducing time and resources overhead during the relay node selection, and improving transmission efficiency.