Embodiments of the present invention provide a method and system for data transmission. The method for data transmission includes: sending, according to a mapping relationship between a first H-RNTI of a user equipment and a second H-RNTI of a relay node accessed by the user equipment, data to the user equipment corresponding to the first H-RNTI by using the relay node corresponding to the second H-RNTI. By using the technical solutions of the embodiments, the coverage capability of a cell edge is enhanced, and the efficiency in transmitting data to a UE at the cell edge is further improved.