A mobile communications method, comprising: receiving, by an access network device by using a terrestrial interface of a first network standard between an access network and a first core network, a first terrestrial interface message of the first network standard sent by the first core network; generating, by the access network device according to an air interface protocol of an air interface of a second network standard between the access network and user equipment, UE, and the first terrestrial interface message, a first air interface message of the second network standard; sending, by the access network device by using the air interface of the second network standard, the first air interface message to the UE; and characterized in determining, by the access network device, the UE is handover from the first core network to a second core network, wherein the terrestrial interface between the second core network and the access network is a terrestrial interface of a third network standard; switching, by the access network device, the UE from the terrestrial interface of the first network standard between the access network and the first core network to the terrestrial interface between the access network and the second core network; receiving, by the access network device by using the terrestrial interface of the third network standard between the access network and the second core network, a second terrestrial interface message of the third network standard sent by the second core network; generating, by the access network device according to the air interface protocol of the air interface of the second network standard and the second terrestrial interface message, a second air interface message of the second network standard; and sending, by the access network device by using the air interface of the second network standard, the second air interface message to the UE. receiving, by an access network device by using a terrestrial interface of a first network standard between an access network and a first core network, a first terrestrial interface message of the first network standard sent by the first core network; generating, by the access network device according to an air interface protocol of an air interface of a second network standard between the access network and user equipment, UE, and the first terrestrial interface message, a first air interface message of the second network standard; sending, by the access network device by using the air interface of the second network standard, the first air interface message to the UE; and characterized in determining, by the access network device, the UE is handover from the first core network to a second core network, wherein the terrestrial interface between the second core network and the access network is a terrestrial interface of a third network standard; switching, by the access network device, the UE from the terrestrial interface of the first network standard between the access network and the first core network to the terrestrial interface between the access network and the second core network; receiving, by the access network device by using the terrestrial interface of the third network standard between the access network and the second core network, a second terrestrial interface message of the third network standard sent by the second core network; generating, by the access network device according to the air interface protocol of the air interface of the second network standard and the second terrestrial interface message, a second air interface message of the second network standard; and sending, by the access network device by using the air interface of the second network standard, the second air interface message to the UE.