In this paper, we propose an optimized polarization filtering based digital self-interference (SI) cancellation (OPC) scheme for full-duplex communication. The proposed OPC scheme utilizes polarization to increase the distinction between the desired signal and the SI and maximizes the signal to interference plus noise ratio (SINR) of the output signal. In order to achieve an optimal trade-off between the desired signal reception and the SI cancellation, an appropriate polarization state (PS) should be selected on the great circle polarization track, which is determined by the PSs of both the SI and the desired signal. Analysis and numerical results demonstrate that the proposed scheme can guarantee that the SINR gain is always positive in the case of any polarization dissimilarity coefficient. In addition, the performance of the OPC scheme can reach the theoretical upper limit in polarization SI cancellation schemes.