A method for determining a data forwarding tunnel, an AMF entity, and a base station (BS) are provided. The method includes: receiving data forwarding information of target UE forwarded by MME, and acquiring a QoS flow configured by a 5G core network for each bearer of the target UE, and mapping relationship between a bearer and a QoS flow, where the data forwarding information includes a list of bearers allocated by EPS to the target UE and an indication of a determination by a 4G BS as to whether each bearer of the target UE has data to forward; transmitting the data forwarding information, the configured QoS flow, and the mapping relationship to a target 5G BS; and receiving forwarding tunnel information of a 5G BS configured for the target UE by the target 5G BS according to the data forwarding information, the configured QoS flow, and the mapping relationship.