A charging method for network system handover, comprising: sending, by a control plane function entity, a charging service establishment message for a 5 th generation, 5G, data connection to a charging function, entity through a service-based interface, SBI, wherein the service establishment request message is used to request to establish an SBI charging session for the 5G data connection; requesting, by the control plane function entity through the SBI charging session, to perform online charging or offline charging in the 5G data connection; receiving, by the control plane function entity, a network handover request to request the terminal to hand over from the 5G data connection to the 4G data connection; and after handover from the 5G data connection to a 4 th generation, 4G, data connection, requesting, by the control plane function entity through the SBI charging session, to perform online charging and/or offline charging in the 4G data connection; characterized in that: during the handover from the 5G data connection to the 4G data connection, the method further comprises: determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is an immediate reporting trigger; and sending, by the control plane function entity, a charging update message to the charging function entity through the SBI charging session, wherein the charging update message comprises network usage information of the 5G data connection and/or a quota request of the 4G data connection after the handover; or determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is a deferred reporting trigger; and stopping, by the control plane function entity, recording network usage information of the 5G data connection, and re-recording network usage information of the 4G data connection after the handover; or determineing, by the control plane function entity, that there is no active 5G handover trigger; combining and recording, by the control plane function entity, network usage information of the 5G data connection and network usage information of the 4G data connection. sending, by a control plane function entity, a charging service establishment message for a 5 th generation, 5G, data connection to a charging function, entity through a service-based interface, SBI, wherein the service establishment request message is used to request to establish an SBI charging session for the 5G data connection; requesting, by the control plane function entity through the SBI charging session, to perform online charging or offline charging in the 5G data connection; receiving, by the control plane function entity, a network handover request to request the terminal to hand over from the 5G data connection to the 4G data connection; and after handover from the 5G data connection to a 4 th generation, 4G, data connection, requesting, by the control plane function entity through the SBI charging session, to perform online charging and/or offline charging in the 4G data connection; characterized in that: during the handover from the 5G data connection to the 4G data connection, the method further comprises: determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is an immediate reporting trigger; and sending, by the control plane function entity, a charging update message to the charging function entity through the SBI charging session, wherein the charging update message comprises network usage information of the 5G data connection and/or a quota request of the 4G data connection after the handover; or determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is a deferred reporting trigger; and stopping, by the control plane function entity, recording network usage information of the 5G data connection, and re-recording network usage information of the 4G data connection after the handover; or determineing, by the control plane function entity, that there is no active 5G handover trigger; combining and recording, by the control plane function entity, network usage information of the 5G data connection and network usage information of the 4G data connection. determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is an immediate reporting trigger; and sending, by the control plane function entity, a charging update message to the charging function entity through the SBI charging session, wherein the charging update message comprises network usage information of the 5G data connection and/or a quota request of the 4G data connection after the handover; or determining (512, 516), by the control plane function entity, that a 5G handover trigger is in an active state, and that a type of the 5G handover trigger is a deferred reporting trigger; and stopping, by the control plane function entity, recording network usage information of the 5G data connection, and re-recording network usage information of the 4G data connection after the handover; or determineing, by the control plane function entity, that there is no active 5G handover trigger; combining and recording, by the control plane function entity, network usage information of the 5G data connection and network usage information of the 4G data connection.