A data transmission or reception method, comprising: receiving, by a terminal device, information, sent by an access network device, about a carrier of the terminal device; determining, by the terminal device based on the information about the carrier, a hybrid automatic repeat request, HARQ, process quantity corresponding to the carrier; and transmitting, by the terminal device, data based on the process quantity corresponding to the carrier, when the data is uplink data, wherein the information about the carrier comprises at least one of the following: a time relationship between uplink scheduling of the terminal device on the carrier and uplink data transmission corresponding to the uplink scheduling, time scheduling unit information of the terminal device on the carrier, a subcarrier spacing of the terminal device on the carrier, and information about a transmission capability of the terminal device on the carrier; or receiving, by the terminal device, data based on the process quantity corresponding to the carrier, when the data is downlink data, wherein the information about the carrier comprises at least one of the following: a time relationship between downlink scheduling of the terminal device on the carrier and downlink data reception corresponding to the downlink scheduling, a time relationship between the downlink data reception of the terminal device on the carrier and sending a feedback message by the terminal device after the terminal device receives the downlink data, time scheduling unit information of the terminal device on the carrier, a subcarrier spacing of the terminal device on the carrier, and information about a transmission capability of the terminal device on the carrier. receiving, by a terminal device, information, sent by an access network device, about a carrier of the terminal device; determining, by the terminal device based on the information about the carrier, a hybrid automatic repeat request, HARQ, process quantity corresponding to the carrier; and transmitting, by the terminal device, data based on the process quantity corresponding to the carrier, when the data is uplink data, wherein the information about the carrier comprises at least one of the following: a time relationship between uplink scheduling of the terminal device on the carrier and uplink data transmission corresponding to the uplink scheduling, time scheduling unit information of the terminal device on the carrier, a subcarrier spacing of the terminal device on the carrier, and information about a transmission capability of the terminal device on the carrier; or receiving, by the terminal device, data based on the process quantity corresponding to the carrier, when the data is downlink data, wherein the information about the carrier comprises at least one of the following: a time relationship between downlink scheduling of the terminal device on the carrier and downlink data reception corresponding to the downlink scheduling, a time relationship between the downlink data reception of the terminal device on the carrier and sending a feedback message by the terminal device after the terminal device receives the downlink data, time scheduling unit information of the terminal device on the carrier, a subcarrier spacing of the terminal device on the carrier, and information about a transmission capability of the terminal device on the carrier.