A data transmission channel processing method, comprising: determining (301, 401, 501, 601, 702), by a session management network element, that a data flow of a packet data unit, PDU, session of a terminal needs to be offloaded, wherein the PDU session is established by using a 3rd generation partnership project, 3GPP, access technology and a non-3GPP access technology; notifying, by the session management network element, the terminal of a transmission policy of the data flow of the PDU session by using an access and mobility management network element, wherein the transmission policy comprises information about the data flow and an access technology type; and determining (302, 402, 503, 602, 703), by the session management network element, to insert an offloading device into a data path of the PDU session, wherein through the offloading device the data flow is offloaded into different data transmission channels, wherein the data path of the PDU session comprises a data transmission channel in the 3GPP access technology and a data transmission channel in the non-3GPP access technology, and wherein the determining (302, 402, 503, 602, 703), by the session management network element, to insert the offloading device into the data path of the PDU session, is based on - a state of the data transmission channel in the 3GPP access technology comprising a user plane active state or a user plane inactive state, and - a state of the data transmission channel in the non-3GPP access technology comprising a user plane active state or a user plane inactive state, wherein if the state of the data transmission channel in the 3GPP access technology is the user plane inactive state, determining, by the session management network element, to insert the offloading device into the data transmission channel in the non-3GPP access technology; or if the state of the data transmission channel in the non-3GPP access technology is the user plane inactive state, determining, by the session management network element, to insert the offloading device into the data transmission channel in the 3GPP access technology. determining (301, 401, 501, 601, 702), by a session management network element, that a data flow of a packet data unit, PDU, session of a terminal needs to be offloaded, wherein the PDU session is established by using a 3rd generation partnership project, 3GPP, access technology and a non-3GPP access technology; notifying, by the session management network element, the terminal of a transmission policy of the data flow of the PDU session by using an access and mobility management network element, wherein the transmission policy comprises information about the data flow and an access technology type; and determining (302, 402, 503, 602, 703), by the session management network element, to insert an offloading device into a data path of the PDU session, wherein through the offloading device the data flow is offloaded into different data transmission channels, wherein the data path of the PDU session comprises a data transmission channel in the 3GPP access technology and a data transmission channel in the non-3GPP access technology, and wherein the determining (302, 402, 503, 602, 703), by the session management network element, to insert the offloading device into the data path of the PDU session, is based on - a state of the data transmission channel in the 3GPP access technology comprising a user plane active state or a user plane inactive state, and - a state of the data transmission channel in the non-3GPP access technology comprising a user plane active state or a user plane inactive state, - a state of the data transmission channel in the 3GPP access technology comprising a user plane active state or a user plane inactive state, and - a state of the data transmission channel in the non-3GPP access technology comprising a user plane active state or a user plane inactive state, if the state of the data transmission channel in the 3GPP access technology is the user plane inactive state, determining, by the session management network element, to insert the offloading device into the data transmission channel in the non-3GPP access technology; or if the state of the data transmission channel in the non-3GPP access technology is the user plane inactive state, determining, by the session management network element, to insert the offloading device into the data transmission channel in the 3GPP access technology.