Disclosed are a data transmission method and device. The method comprises: receiving a PDCCH, wherein the PDCCH comprises an indication domain which can at least indicate different HARQ processes the number of which is a sum of maximum HARQ process numbers of a plurality of carriers, and initial transmission and retransmission of data in the same HARQ process use different carriers; and receiving data scheduled by the PDCCH according to the PDCCH. By means of the present application, transmission carriers during initial transmission and retransmission of data in the same process can be adjusted flexibly, so that, when interferences to some carrier(s) are serious, data transmission in the process is adjusted to a carrier or carriers to which interference conditions are not serious, so as to improve system transmission efficiency.