A method for updating an identifier, comprising: during a process when a first terminal transmits data carrying a first identifier to a second terminal, acquiring, by the first terminal, a second identifier, wherein the second identifier is configured to update the first identifier, and both the first identifier and the second identifier are configured to identify the first terminal; and transmitting, by the first terminal, indication information to the second terminal, wherein the indication information is configured to indicate that the second identifier carried in data transmitted subsequently by the first terminal to the second terminal is an update of the first identifier, characterized in that, the indication information comprises the first identifier and the second identifier, the first identifier comprises a first Media Access Control, MAC, layer identifier and a first physical, PHY, layer identifier, the second identifier comprises a second MAC layer identifier and a second PHY layer identifier, the second MAC layer identifier is configured to update the first MAC layer identifier and the second PHY layer identifier is configured to update the first PHY layer identifier, and wherein transmitting, by the first terminal, the indication information to the second terminal comprises: generating, by the first terminal, an MAC Protocol Data Unit, PDU, wherein an MAC Control Element, CE, in the MAC PDU carries the second MAC layer identifier, another MAC CE in the MAC PDU carries the second PHY layer identifier, and an MAC subheader in the MAC PDU carries the first MAC layer identifier; encoding and modulating, by the first terminal, the first PHY layer identifier and the MAC PDU to obtain data carrying the first identifier and the second identifier; and transmitting, by the first terminal, the data carrying the first identifier and the second identifier to the second terminal. during a process when a first terminal transmits data carrying a first identifier to a second terminal, acquiring, by the first terminal, a second identifier, wherein the second identifier is configured to update the first identifier, and both the first identifier and the second identifier are configured to identify the first terminal; and transmitting, by the first terminal, indication information to the second terminal, wherein the indication information is configured to indicate that the second identifier carried in data transmitted subsequently by the first terminal to the second terminal is an update of the first identifier, characterized in that, the indication information comprises the first identifier and the second identifier, the first identifier comprises a first Media Access Control, MAC, layer identifier and a first physical, PHY, layer identifier, the second identifier comprises a second MAC layer identifier and a second PHY layer identifier, the second MAC layer identifier is configured to update the first MAC layer identifier and the second PHY layer identifier is configured to update the first PHY layer identifier, and wherein transmitting, by the first terminal, the indication information to the second terminal comprises: generating, by the first terminal, an MAC Protocol Data Unit, PDU, wherein an MAC Control Element, CE, in the MAC PDU carries the second MAC layer identifier, another MAC CE in the MAC PDU carries the second PHY layer identifier, and an MAC subheader in the MAC PDU carries the first MAC layer identifier; encoding and modulating, by the first terminal, the first PHY layer identifier and the MAC PDU to obtain data carrying the first identifier and the second identifier; and transmitting, by the first terminal, the data carrying the first identifier and the second identifier to the second terminal. generating, by the first terminal, an MAC Protocol Data Unit, PDU, wherein an MAC Control Element, CE, in the MAC PDU carries the second MAC layer identifier, another MAC CE in the MAC PDU carries the second PHY layer identifier, and an MAC subheader in the MAC PDU carries the first MAC layer identifier; encoding and modulating, by the first terminal, the first PHY layer identifier and the MAC PDU to obtain data carrying the first identifier and the second identifier; and transmitting, by the first terminal, the data carrying the first identifier and the second identifier to the second terminal.