Embodiments of this application provide a data transmission method and device. The method includes: obtaining, by a first access network device, a first message from a second access network device, where the first message requests context information of a terminal device; and sending, by the first access network device, a data packet to the second access network device. The first access network device is a corresponding access network device of the terminal device before the re-establishment procedure, and the second access network device is a corresponding access network device when the terminal device initiates the re-establishment procedure.