A CSI feedback method, a CSI acquisition method, a CSI feedback device and a CSI acquisition device are provided, so as to reduce pilot resources configured for a UE and reduce the difficulty in processing CSI progresses at a UE side, thereby to facilitate the CSI feedback and acquisition and save resources. The CSI acquisition method includes steps of: determining beamforming array information in a first dimension; beamforming a pilot signal in a second dimension in accordance with the beamforming array information in the first dimension, and transmitting the beamformed pilot signal in the second dimension to a UE through a pilot resource in the second dimension; and receiving, from the UE, CSI in the second dimension obtained by measuring the pilot signal in the second dimension.