  We investigate the possibility of detecting hidden vector gauge bosons at ILC
linear collider. The study is performed in the framework of hidden sector
extension of Standard Model with 3 degenerate dark gauge bosons. By studying
the cross section of pair dark gauge boson with photon at initial state
radiation we found that at the energy $\sqrt{s} \approx$ 1300 GeV the cross
section can be as large as $48fb$, the same order ($\mathcal{O}(fb)$) with the
irreducible background of the Standard Model. Hence more methods needed to be
done to eliminate the background for this model.
