A channel quality indicator feedback method, comprising: receiving data (S31, S41) by a terminal device from a network side device; determining (S32, S43, S47), by the terminal device, a response message of data, wherein the response message comprises an acknowledgement message or a negative acknowledgement message; determining (S33, S44, S48), by the terminal device, first channel state information of a downlink channel corresponding to the data; and sending, by the terminal device, the response message and the first channel state information to the network side device for adjusting a modulation and coding scheme for subsequent data transmissions based on the response message and the first channel state information, wherein a higher modulation and coding scheme level has a higher transmission bit rate, characterised in that the acknowledgement message indicates that a direction for adjusting the modulation and coding scheme by the network side device is increasing a level of the modulation and coding scheme, and the negative acknowledgement message indicates that the direction for adjusting the modulation and coding scheme by the network side device is reducing the level of the modulation and coding scheme; and the first channel state information indicates an offset of adjusting the level of the modulation and coding scheme in accordance with the direction of adjusting the modulation and coding scheme indicated by the response message of the data, wherein a value of the first channel state information being 0 indicates that the level of the modulation and coding scheme is to be adjusted by one level, and the value of the first channel state information being 1 indicates that the level of the modulation and coding scheme is to be adjusted by two levels. receiving data (S31, S41) by a terminal device from a network side device; determining (S32, S43, S47), by the terminal device, a response message of data, wherein the response message comprises an acknowledgement message or a negative acknowledgement message; determining (S33, S44, S48), by the terminal device, first channel state information of a downlink channel corresponding to the data; and sending, by the terminal device, the response message and the first channel state information to the network side device for adjusting a modulation and coding scheme for subsequent data transmissions based on the response message and the first channel state information, wherein a higher modulation and coding scheme level has a higher transmission bit rate, characterised in that the acknowledgement message indicates that a direction for adjusting the modulation and coding scheme by the network side device is increasing a level of the modulation and coding scheme, and the negative acknowledgement message indicates that the direction for adjusting the modulation and coding scheme by the network side device is reducing the level of the modulation and coding scheme; and the first channel state information indicates an offset of adjusting the level of the modulation and coding scheme in accordance with the direction of adjusting the modulation and coding scheme indicated by the response message of the data, wherein a value of the first channel state information being 0 indicates that the level of the modulation and coding scheme is to be adjusted by one level, and the value of the first channel state information being 1 indicates that the level of the modulation and coding scheme is to be adjusted by two levels.