A data transmission method, comprising: sending, by a network device, first configuration information to a terminal device, wherein the first configuration information comprises first carrier configuration information and first time configuration information, the first carrier configuration information indicates more than one carrier configured by the network device for a bearer for performing hybrid automatic repeat request, HARQ, and the first time configuration information indicates a first transmission time unit bundling quantity corresponding to each of the more than one carrier, wherein the first transmission time unit bundling quantity indicates an amount of transmission time units corresponding to each of the more than one carrier; and sending or receiving, by the network device, data corresponding to the bearer based on the first carrier configuration information and the first time configuration information, wherein the sending or receiving data corresponding to the bearer comprises: sending or receiving, by the network device, different redundancy versions of the same data on the more than one carrier based on the first carrier configuration information and the first time configuration information, wherein the first configuration information further comprises a grant free transmission configuration, and the grant free transmission configuration comprises a minimum value of a total quantity of transmission time units required each time grant free transmission is performed on the bearer and a maximum value of a bundling quantity of transmission time units allowing transmission on each carrier. sending, by a network device, first configuration information to a terminal device, wherein the first configuration information comprises first carrier configuration information and first time configuration information, the first carrier configuration information indicates more than one carrier configured by the network device for a bearer for performing hybrid automatic repeat request, HARQ, and the first time configuration information indicates a first transmission time unit bundling quantity corresponding to each of the more than one carrier, wherein the first transmission time unit bundling quantity indicates an amount of transmission time units corresponding to each of the more than one carrier; and sending or receiving, by the network device, data corresponding to the bearer based on the first carrier configuration information and the first time configuration information, wherein the sending or receiving data corresponding to the bearer comprises: sending or receiving, by the network device, different redundancy versions of the same data on the more than one carrier based on the first carrier configuration information and the first time configuration information, wherein the first configuration information further comprises a grant free transmission configuration, and the grant free transmission configuration comprises a minimum value of a total quantity of transmission time units required each time grant free transmission is performed on the bearer and a maximum value of a bundling quantity of transmission time units allowing transmission on each carrier. sending or receiving, by the network device, different redundancy versions of the same data on the more than one carrier based on the first carrier configuration information and the first time configuration information, wherein the first configuration information further comprises a grant free transmission configuration, and the grant free transmission configuration comprises a minimum value of a total quantity of transmission time units required each time grant free transmission is performed on the bearer and a maximum value of a bundling quantity of transmission time units allowing transmission on each carrier.