A method for transmitting downlink data, the method comprising: receiving, by a first device, data of a scheduled terminal, a resource allocation scheme of the scheduled terminal, and a beam-forming vector or a pre-coding matrix used by the scheduled terminal in the resource allocation scheme, transmitted by a second device via a fronthaul interface, wherein the data of the scheduled terminal are data obtained by the second device via performing first space-domain preprocessing on baseband data of the scheduled terminal; wherein the first space-domain preprocessing at least comprises: scrambling and modulating the baseband data of the scheduled terminal, and mapping the data of the scheduled terminal to a plurality of data layers according to a number of parallel data streams which can be supported; performing, by the first device, second space-domain preprocessing on the data of the scheduled terminal; and converting, by the first device, data obtained as a result of the second space-domain preprocessing into a radio frequency signal, and transmitting the radio frequency signal; wherein the performing, by the first device, the second space-domain preprocessing on the data of the scheduled terminal comprises: mapping, by the first device, the data of the scheduled terminal from data layers to reference signal ports according to a mapping relationship between the data layers and the reference signal ports, and performing beam-forming on the data of the scheduled terminal using the beam-forming vector, or performing pre-coding processing on the data of the scheduled terminal using the pre-coding matrix, and mapping beam-formed or pre-coded data of the scheduled terminal to a sub-carrier. receiving, by a first device, data of a scheduled terminal, a resource allocation scheme of the scheduled terminal, and a beam-forming vector or a pre-coding matrix used by the scheduled terminal in the resource allocation scheme, transmitted by a second device via a fronthaul interface, wherein the data of the scheduled terminal are data obtained by the second device via performing first space-domain preprocessing on baseband data of the scheduled terminal; wherein the first space-domain preprocessing at least comprises: scrambling and modulating the baseband data of the scheduled terminal, and mapping the data of the scheduled terminal to a plurality of data layers according to a number of parallel data streams which can be supported; performing, by the first device, second space-domain preprocessing on the data of the scheduled terminal; and converting, by the first device, data obtained as a result of the second space-domain preprocessing into a radio frequency signal, and transmitting the radio frequency signal; wherein the performing, by the first device, the second space-domain preprocessing on the data of the scheduled terminal comprises: mapping, by the first device, the data of the scheduled terminal from data layers to reference signal ports according to a mapping relationship between the data layers and the reference signal ports, and performing beam-forming on the data of the scheduled terminal using the beam-forming vector, or performing pre-coding processing on the data of the scheduled terminal using the pre-coding matrix, and mapping beam-formed or pre-coded data of the scheduled terminal to a sub-carrier.