Embodiments of the present invention provide a baseband processing unit, a radio remote unit, and a communication method. The baseband processing unit includes: a millimeter wave band transceiver, configured to receive an interface signal sent by a radio remote unit by using a millimeter wave band; an interface signal processing module, configured to convert the interface signal received by the millimeter wave band transceiver into uplink baseband data; and a baseband data processing module, configured to: process the uplink baseband data to obtain an uplink baseband signal, and send the uplink baseband signal to a gateway. In the embodiments of the present invention, the baseband processing unit and the radio remote unit may communicate by using the millimeter wave band, thereby saving optical fiber resources.