A data flow transmission method, applied to a wireless network system, comprising: obtaining, by a first network device, position information of a user equipment for which the first network device provides a service; determining, by the first network device, a quantity of user equipments in wireless network coverage according to the position information; when the quantity of user equipments in the wireless network coverage is less than a first threshold, determining, by the first network device according to the position information, a quantity of remote user equipments in a first group connected to a relay user equipment, wherein the remote user equipments are user equipments located outside the wireless network coverage; when the quantity of the remote user equipments in the first group connected to the relay user equipment is greater than or equal to a second threshold, determining, by the first network device, to send data of the remote user equipments by using a common data flow bearer of a unicast mode, and triggering, by the first network device, the relay user equipment to establish the common data flow bearer with a second network device, wherein the common data flow bearer is used to carry a data flow transmitted from the second network device to a remote user equipment in the first group, the remote user equipment in the first group is connected to the second network device by using the relay user equipment; and sending, by the first network device, an identifier of a common data flow to the remote user equipment in the first group by using the relay user equipment, wherein the identifier of the common data flow is used to instruct the remote user equipment in the first group to receive data of the common data flow, the common data flow is the data flow transmitted from the second network device to the remote user equipment in the first group. obtaining, by a first network device, position information of a user equipment for which the first network device provides a service; determining, by the first network device, a quantity of user equipments in wireless network coverage according to the position information; when the quantity of user equipments in the wireless network coverage is less than a first threshold, determining, by the first network device according to the position information, a quantity of remote user equipments in a first group connected to a relay user equipment, wherein the remote user equipments are user equipments located outside the wireless network coverage; when the quantity of the remote user equipments in the first group connected to the relay user equipment is greater than or equal to a second threshold, determining, by the first network device, to send data of the remote user equipments by using a common data flow bearer of a unicast mode, and triggering, by the first network device, the relay user equipment to establish the common data flow bearer with a second network device, wherein the common data flow bearer is used to carry a data flow transmitted from the second network device to a remote user equipment in the first group, the remote user equipment in the first group is connected to the second network device by using the relay user equipment; and sending, by the first network device, an identifier of a common data flow to the remote user equipment in the first group by using the relay user equipment, wherein the identifier of the common data flow is used to instruct the remote user equipment in the first group to receive data of the common data flow, the common data flow is the data flow transmitted from the second network device to the remote user equipment in the first group.