The invention provides a locomotive reconnection communication device and a control method. The device comprises an LON channel unit and a channel control unit, wherein the LON channel unit is connected to a train LON and used for completing communication protocol conversion between the locomotive reconnection communication device and the train LON; the channel control unit is connected with the LON channel unit so as to control the working state of the LON channel unit. The LON channel unit comprises a main LON channel and a standby LON channel. The channel control unit selects one channel as the service channel and conducts two-way data exchange with the train LON through the service channel. The method comprises the steps that access signs used for indicating the working state of the LON channel are preset for a corresponding data buffer of the main LON channel and a corresponding data buffer of the standby LON channel; the service channel is selected according to the access signs and used for conducting data exchange with the train LON.