A data transmission method, wherein the method comprises: receiving (S412, S510, S614, S711), by a first user plane function entity, a data packet from a first terminal through an uplink path corresponding to the first terminal, wherein the data packet carries addressing information of a second terminal, and the first user plane function entity is a user plane function entity currently accessed by the first terminal; determining (S413-S414, S511-S514, S615-S616, S712-S715), by the first user plane function entity, path information of a second user plane function entity based on information about the uplink path corresponding to the first terminal and the addressing information of the second terminal, wherein the second user plane function entity is a user plane function entity currently accessed by the second terminal, the information about the uplink path corresponding to the first terminal comprise a tunnel identifier of the first user plane function entity allocated for the first terminal and the path information of the second user plane function entity comprise a tunnel identifier of the second user plane function entity; and sending (S415, S515, S617, S716), by the first user plane function entity, the data packet to the second user plane function entity based on the path information of the second user plane function entity; said method being characterized in that the step of determining, by the first user plane function entity, path information of a second user plane function entity based on information about the uplink path corresponding to the first terminal and the addressing information of the second terminal comprises: determining (S413, S511, S615, S712), by the first user plane function entity based on the information about the uplink path corresponding to the first terminal, an identity of a mobile local area network, MLAN, to which the first terminal subscribes, wherein the identity of the MLAN to which the first terminal subscribes is the same as an identity of a MLAN to which the second terminal subscribes and the MLAN provides a LAN service based on a mobile network; and determining (S414, S512-S514, S616, S713-S715), by the first user plane function entity, the path information of the second user plane function entity based on the identity of the MLAN and the addressing information of the second terminal. receiving (S412, S510, S614, S711), by a first user plane function entity, a data packet from a first terminal through an uplink path corresponding to the first terminal, wherein the data packet carries addressing information of a second terminal, and the first user plane function entity is a user plane function entity currently accessed by the first terminal; determining (S413-S414, S511-S514, S615-S616, S712-S715), by the first user plane function entity, path information of a second user plane function entity based on information about the uplink path corresponding to the first terminal and the addressing information of the second terminal, wherein the second user plane function entity is a user plane function entity currently accessed by the second terminal, the information about the uplink path corresponding to the first terminal comprise a tunnel identifier of the first user plane function entity allocated for the first terminal and the path information of the second user plane function entity comprise a tunnel identifier of the second user plane function entity; and sending (S415, S515, S617, S716), by the first user plane function entity, the data packet to the second user plane function entity based on the path information of the second user plane function entity; said method being characterized in that the step of determining, by the first user plane function entity, path information of a second user plane function entity based on information about the uplink path corresponding to the first terminal and the addressing information of the second terminal comprises: determining (S413, S511, S615, S712), by the first user plane function entity based on the information about the uplink path corresponding to the first terminal, an identity of a mobile local area network, MLAN, to which the first terminal subscribes, wherein the identity of the MLAN to which the first terminal subscribes is the same as an identity of a MLAN to which the second terminal subscribes and the MLAN provides a LAN service based on a mobile network; and determining (S414, S512-S514, S616, S713-S715), by the first user plane function entity, the path information of the second user plane function entity based on the identity of the MLAN and the addressing information of the second terminal. determining (S413, S511, S615, S712), by the first user plane function entity based on the information about the uplink path corresponding to the first terminal, an identity of a mobile local area network, MLAN, to which the first terminal subscribes, wherein the identity of the MLAN to which the first terminal subscribes is the same as an identity of a MLAN to which the second terminal subscribes and the MLAN provides a LAN service based on a mobile network; and determining (S414, S512-S514, S616, S713-S715), by the first user plane function entity, the path information of the second user plane function entity based on the identity of the MLAN and the addressing information of the second terminal.