A method for reporting a channel state for a downlink channel to be transmitted via at least one two-dimensional array antenna element composed of a row antenna array and a column antenna array is disclosed in accordance with one embodiment of the present invention. The method is performed by a terminal, and the method may comprise the steps of: receiving settings for channel state information (CSI) process 1 and CSI process 2, the CSI process 1 and the CSI process 2 each comprising a plurality of CSI-reference signal (RS) settings; selecting one of the CSI process 1 and the CSI process 2 if the CSI process 1 and the CSI process 2 have the same feedback cycle and offset; and estimating the downlink channel and reporting the channel estimation to a serving base station according to one selected from the CSI process 1 and the CSI process 2.