  The results of mixing angle measurement for $\eta'$, $\eta$ mesons generated
in charge exchange reactions with $\pi^{-}$ and $K^{-}$ beams are preseneted.
When the $\eta'$, $\eta$ mesons are described in nonstrange(NS)--strange(S)
quark basis the $\pi^{-}$ and $K^{-}$ beams allow to study $|\eta_{q}>$ and
$|\eta_{s}>$ parts of the meson wave function. The cross section ratio at
$t'=0$ (GeV/c)$^{2}$ in the $\pi^{-}$ beam is $R_{\pi}(\eta'/\eta)= 0.56 \pm
0.04$, results in mixing angle $\phi_{P} = (36.8 \pm 1.)^{o} $. For $K^{-}$
beam the ratio is $R_{K}(\eta'/\eta)= 1.30 \pm 0.16$. It was found that
gluonium content in $\eta'$ is $\sin^{2}\psi_{G}= 0.15 \pm 0.06$. The
experiment was carried out with GAMS-4$\pi$ Setup.
