A data transmission method and a communication device are provided. The method includes: determining, by a packet data convergence protocol (PDCP) entity, the number of copies of duplicated PDCP protocol data unit (PDU); determining, by the PDCP entity, a first radio link layer control protocol (RLC) entity transmitting the PDCP PDU according to indication information; and transmitting, by the PDCP entity, the PDCP PDU to the first RLC entity. According to the data transmission method and the communication device of the embodiments of the disclosure, data duplication and transmission at a PDCP layer may be implemented.