A channel management method and device for a wireless local area network in rail transport, and a wireless local area network system in rail transport are provided. The method includes: determining, by a controller, a to-be-changed trackside access point (AP) for a first vehicle, where the to-be-changed trackside AP for the first vehicle is behind the first vehicle, and a distance of the to-be-changed trackside AP to the first vehicle exceeds a preset threshold; instructing, by the controller, the to-be-changed trackside AP to change an operating channel from an operating channel of a first vehicle-mounted AP on the first vehicle to an operating channel of a second vehicle-mounted AP on a second vehicle, where the second vehicle is a vehicle following the first vehicle. Because operating channels of two vehicle-mounted APs are different, interference between vehicle-mounted APs on one vehicle and a next vehicle is low. Moreover, a trackside AP behind a previous vehicle is instructed to change a channel, so that a vehicle-mounted AP does not need to change a channel. Therefore, a handover time is short.