A method for obtaining downlink channel information, comprising: performing, by a network side device, precoding weighting on M channel state information-reference signals, CSI-RSs, of each of N sub-cycles in a cycle, wherein each sub-cycle is a quantity of measurement pilot subframes for bearing and transmitting the M CSI-RSs, N is a positive integer, and M is a quantity of CSI-RSs required by a predetermined antenna quantity; sending, by the network side device, the M weighted CSI-RSs of each sub-cycle to user equipment, UE; receiving, by the network side device, M precoding matrix indicators, PMIs, and M channel quality indicators, CQIs, that are sent by the UE and that correspond to the M CSI-RSs of each sub-cycle, wherein the M PMIs and the M CQIs are obtained by the UE by separately measuring the M weighted CSI-RSs based on a set of rank 1 precoding codebooks corresponding to the predetermined antenna quantity; obtaining, by the network side device, M signal-to-noise ratios of a downlink channel of the UE according to the M CQIs of each sub-cycle; obtaining, by the network side device, M equivalent codebooks according to the M PMIs of each sub-cycle and weights of the precoding weighting; and obtaining, by the network side device, according to the M signal-to-noise ratios of the downlink channel and the M equivalent codebooks, a covariance matrix of the downlink channel of the UE as the downlink channel information; wherein after the obtaining a covariance matrix of the downlink channel according to the M signal-to-noise ratios of the downlink channel and the M equivalent codebooks, the method further comprises: performing, by the network side device, beamforming weighting processing on downlink data of the UE according to the covariance matrix. performing, by a network side device, precoding weighting on M channel state information-reference signals, CSI-RSs, of each of N sub-cycles in a cycle, wherein each sub-cycle is a quantity of measurement pilot subframes for bearing and transmitting the M CSI-RSs, N is a positive integer, and M is a quantity of CSI-RSs required by a predetermined antenna quantity; sending, by the network side device, the M weighted CSI-RSs of each sub-cycle to user equipment, UE; receiving, by the network side device, M precoding matrix indicators, PMIs, and M channel quality indicators, CQIs, that are sent by the UE and that correspond to the M CSI-RSs of each sub-cycle, wherein the M PMIs and the M CQIs are obtained by the UE by separately measuring the M weighted CSI-RSs based on a set of rank 1 precoding codebooks corresponding to the predetermined antenna quantity; obtaining, by the network side device, M signal-to-noise ratios of a downlink channel of the UE according to the M CQIs of each sub-cycle; obtaining, by the network side device, M equivalent codebooks according to the M PMIs of each sub-cycle and weights of the precoding weighting; and obtaining, by the network side device, according to the M signal-to-noise ratios of the downlink channel and the M equivalent codebooks, a covariance matrix of the downlink channel of the UE as the downlink channel information; wherein after the obtaining a covariance matrix of the downlink channel according to the M signal-to-noise ratios of the downlink channel and the M equivalent codebooks, the method further comprises: performing, by the network side device, beamforming weighting processing on downlink data of the UE according to the covariance matrix.