Embodiments of this application disclose a data processing method and a device, so that a controller can also participate in a procedure of electing an active switch, thereby avoiding a problem in the prior art caused by a registration failure when an active switch determined by means of switch election registers with a controller, and improving active switch election efficiency. The method in the embodiments of this application includes: receiving, by a controller, registration requests of multiple switches in a same stack system, where the multiple switches include a target switch; and if the controller determines that the target switch meets a registration success condition, sending, by the controller, a registration success message to the target switch, and selecting the target switch as an active switch.