  A non-Hermitian topological insulator with real spectrum is interesting in
the theory of non-Hermitian extension of topological systems. We find an
experimentally realizable example of a two dimensional non-Hermitian
topological insulator with real spectrum. We consider two-dimensional
Su-Schrieffer-Heeger (SSH) model with gain and loss. We introduce non-Hermitian
polarization vector to explore topological phase and show that topological edge
states in the band gap exist in the system.
