A method and an apparatus for acquiring channel information in a polarization division duplex system. An uplink signal transmitted from a terminal is received, the uplink signal indicating that a null subcarrier is disposed in a first subcarrier overlapped with a second subcarrier including a downlink pilot signal, and a self-interference channel is estimated by using a signal received from the null subcarrier. A signal corresponding to the null subcarrier from the uplink signal is removed, and channel information is acquired by estimating the uplink channel based on estimation results of the self-interference channel and a pilot signal included in the uplink signal from which the null subcarrier is removed.