A method for transmitting data, characterized by comprising: receiving, by an access network device, a first data packet sent by a core network device; determining, by the access network device, a state that a terminal device needs to be in for receiving the first data packet, wherein the state that the terminal device needs to be in is any one of at least two states, and the at least two states are different states in which the terminal device needs to be when performing data transmission with a network side device; sending, by the access network device, indication information to the terminal device, wherein the indication information is used to indicate the state that the terminal device needs to be in for receiving the first data packet; sending, by the access network device, the first data packet to the terminal device; wherein the at least two states comprise a first state and a second state; in the first state, the terminal device and the access network device keep connected, the terminal device and the access network device store context information of the terminal device, and when the terminal device moves within coverage ranges of all access network devices in an access network device set to which the access network device belongs, the terminal device performs a cell reselection process, and the terminal device does not perform handover between access network devices when the terminal device moves from one cell to another; in the second state, the terminal device and the access network device keep connected, when the terminal device moves within the coverage ranges of all access network devices in the access network device set to which the access network device belongs, the access network device controls the terminal device to perform handover between access network devices when the terminal device moves from one cell to another, wherein the method further comprises: acquiring, by the access network device, information of a bearer corresponding to the first data packet or information of a data stream corresponding to the first data packet from the core network device; wherein, determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet comprises: determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet according to the information of the bearer or the information of the data stream. receiving, by an access network device, a first data packet sent by a core network device; determining, by the access network device, a state that a terminal device needs to be in for receiving the first data packet, wherein the state that the terminal device needs to be in is any one of at least two states, and the at least two states are different states in which the terminal device needs to be when performing data transmission with a network side device; sending, by the access network device, indication information to the terminal device, wherein the indication information is used to indicate the state that the terminal device needs to be in for receiving the first data packet; sending, by the access network device, the first data packet to the terminal device; wherein the at least two states comprise a first state and a second state; in the first state, the terminal device and the access network device keep connected, the terminal device and the access network device store context information of the terminal device, and when the terminal device moves within coverage ranges of all access network devices in an access network device set to which the access network device belongs, the terminal device performs a cell reselection process, and the terminal device does not perform handover between access network devices when the terminal device moves from one cell to another; in the second state, the terminal device and the access network device keep connected, when the terminal device moves within the coverage ranges of all access network devices in the access network device set to which the access network device belongs, the access network device controls the terminal device to perform handover between access network devices when the terminal device moves from one cell to another, wherein the method further comprises: acquiring, by the access network device, information of a bearer corresponding to the first data packet or information of a data stream corresponding to the first data packet from the core network device; wherein, determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet comprises: determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet according to the information of the bearer or the information of the data stream. acquiring, by the access network device, information of a bearer corresponding to the first data packet or information of a data stream corresponding to the first data packet from the core network device; wherein, determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet comprises: determining, by the access network device, the state that the terminal device needs to be in for receiving the first data packet according to the information of the bearer or the information of the data stream.