A communication method for sending data from a network side device to a dual-card user equipment UE, comprising: receiving, by a first network side device, an access request from the dual-card UE, and establishing a first bearer according to the access request, wherein the first network side device provides a service for a first card of the dual-card UE, and the first bearer is a data transmission channel between the first network side device and the first card of the dual-card UE; acquiring, by the first network side device, association information recorded by the first card of the dual-card UE between the first card of the dual-card UE and a second card of the dual-card UE, wherein the association information comprises an identifier of the second card of the dual-card UE and an address of a core network entity with which the second card of the dual-card UE is registered, wherein the first card of the dual-card UE and the second card of the dual-card UE belong to different PLMNs; establishing, by the first network side device, a second bearer according to the association information, wherein the second bearer is a data transmission channel between the first network side device and the second card of the dual-card UE, wherein the second bearer is established via a network side device to which the second card of the dual-card UE belongs; splitting, by the first network side device, first data to be transmitted to the dual-card UE into second data and third data; and sending, by the first network side device, the second data to the dual-card UE by using the first bearer, and sending the third data to the dual-card UE by using the second bearer, so that the dual-card UE combines the second data and the third data into the first data. receiving, by a first network side device, an access request from the dual-card UE, and establishing a first bearer according to the access request, wherein the first network side device provides a service for a first card of the dual-card UE, and the first bearer is a data transmission channel between the first network side device and the first card of the dual-card UE; acquiring, by the first network side device, association information recorded by the first card of the dual-card UE between the first card of the dual-card UE and a second card of the dual-card UE, wherein the association information comprises an identifier of the second card of the dual-card UE and an address of a core network entity with which the second card of the dual-card UE is registered, wherein the first card of the dual-card UE and the second card of the dual-card UE belong to different PLMNs; establishing, by the first network side device, a second bearer according to the association information, wherein the second bearer is a data transmission channel between the first network side device and the second card of the dual-card UE, wherein the second bearer is established via a network side device to which the second card of the dual-card UE belongs; splitting, by the first network side device, first data to be transmitted to the dual-card UE into second data and third data; and sending, by the first network side device, the second data to the dual-card UE by using the first bearer, and sending the third data to the dual-card UE by using the second bearer, so that the dual-card UE combines the second data and the third data into the first data.