  The breakdown of the conventional bulk-boundary correspondence due to
non-Hermitian skin effect leads to the non-Bloch bulk-boundary correspondence
in the generalized Brillouin zone. Inspired by the case of the equivalence
between the non-reciprocal hopping and imaginary gauge field, we propose a
method to construct the topological equivalent models of the non-Hermitian
dimerized lattices with the similarity transformations. The idea of the
constructions is from that the imaginary magnetic flux vanishes under the open
boundary condition and the period boundary spectra can be well approximated by
open boundary spectra. As an illustration, we apply this approach to several
representative non-Hermitian SSH models, efficiently obtaining topological
invariants in analytic form defined in the conventional Bloch bands. The method
gives an alternative way to study the topological properties of non-Hermitian
system.
