A method for dynamically indicating a Quality of Service, QoS, Flow Identity, ID, QFI, comprising: obtaining, by User Equipment, UE, a Service Data Adaptation Protocol, SDAP, Service Data Unit, SDU, and obtaining a first QFI to which the SDAP SDU belongs; characterized by further comprising: mapping, by the UE, the first QFI to a second QFI, comprising: when a first threshold is 63: when a value of the first QFI is less than or equal to the first threshold, mapping, by the UE, the value of the first QFI to a value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than the first threshold, mapping, by the UE, the value of the first QFI to a value of an unmapped vacant position of the second QFI; when a first threshold is 64: when the value of the first QFI is less than the first threshold, mapping, by the UE, the value of the first QFI to the value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than or equal to the first threshold, mapping, by the UE, the value of the first QFI to the value of the unmapped vacant position of the second QFI; and comprising, by the UE, the second QFI in an SDAP header, wherein a number of bits of the first QFI is greater than a number of bits of the second QFI. obtaining, by User Equipment, UE, a Service Data Adaptation Protocol, SDAP, Service Data Unit, SDU, and obtaining a first QFI to which the SDAP SDU belongs; characterized by further comprising: mapping, by the UE, the first QFI to a second QFI, comprising: when a first threshold is 63: when a value of the first QFI is less than or equal to the first threshold, mapping, by the UE, the value of the first QFI to a value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than the first threshold, mapping, by the UE, the value of the first QFI to a value of an unmapped vacant position of the second QFI; when a first threshold is 64: when the value of the first QFI is less than the first threshold, mapping, by the UE, the value of the first QFI to the value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than or equal to the first threshold, mapping, by the UE, the value of the first QFI to the value of the unmapped vacant position of the second QFI; and comprising, by the UE, the second QFI in an SDAP header, wherein a number of bits of the first QFI is greater than a number of bits of the second QFI. when a first threshold is 63: when a value of the first QFI is less than or equal to the first threshold, mapping, by the UE, the value of the first QFI to a value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than the first threshold, mapping, by the UE, the value of the first QFI to a value of an unmapped vacant position of the second QFI; when a value of the first QFI is less than or equal to the first threshold, mapping, by the UE, the value of the first QFI to a value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than the first threshold, mapping, by the UE, the value of the first QFI to a value of an unmapped vacant position of the second QFI; when a first threshold is 64: when the value of the first QFI is less than the first threshold, mapping, by the UE, the value of the first QFI to the value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than or equal to the first threshold, mapping, by the UE, the value of the first QFI to the value of the unmapped vacant position of the second QFI; and when the value of the first QFI is less than the first threshold, mapping, by the UE, the value of the first QFI to the value of the second QFI which is the same as the value of the first QFI; when the value of the first QFI is greater than or equal to the first threshold, mapping, by the UE, the value of the first QFI to the value of the unmapped vacant position of the second QFI; and comprising, by the UE, the second QFI in an SDAP header, wherein a number of bits of the first QFI is greater than a number of bits of the second QFI.