A session management method, comprising: when establishing (Step 201) a guaranteed bit rate, GBR, flow of a terminal device in a first communications system, determining (Step 202), by a session management network element in the first communications system based on an operator policy that the GBR flow is a GBR flow needed for handing over the terminal device from the first communications system to a second communications system; and establishing (Step 203), by the session management network element for the GBR flow, a session context corresponding to the second communications system; wherein the determining, by the session management network element based on the operator policy that the GBR flow is a GBR flow needed for handing over the terminal device from the first communications system to the second communications system, comprises: determining, by the session management network element, whether a service type corresponding to the GBR QoS flow is a service type supported by an operator policy of the second communications system; wherein the establishing, by the session management network element for the GBR flow, the session context corresponding to the second communications system, comprises: establishing, by the session management network element, a bearer ID in the second communications system for the GBR flow; wherein the first communications system is a fifth generation, 5G, communications system, and the second communications system is a fourth generation, 4G, communications system. when establishing (Step 201) a guaranteed bit rate, GBR, flow of a terminal device in a first communications system, determining (Step 202), by a session management network element in the first communications system based on an operator policy that the GBR flow is a GBR flow needed for handing over the terminal device from the first communications system to a second communications system; and establishing (Step 203), by the session management network element for the GBR flow, a session context corresponding to the second communications system; wherein the determining, by the session management network element based on the operator policy that the GBR flow is a GBR flow needed for handing over the terminal device from the first communications system to the second communications system, comprises: determining, by the session management network element, whether a service type corresponding to the GBR QoS flow is a service type supported by an operator policy of the second communications system; wherein the establishing, by the session management network element for the GBR flow, the session context corresponding to the second communications system, comprises: establishing, by the session management network element, a bearer ID in the second communications system for the GBR flow; wherein the first communications system is a fifth generation, 5G, communications system, and the second communications system is a fourth generation, 4G, communications system. establishing, by the session management network element, a bearer ID in the second communications system for the GBR flow; wherein the first communications system is a fifth generation, 5G, communications system, and the second communications system is a fourth generation, 4G, communications system.