  We study the radiative decays $h_{c}\rightarrow\gamma\eta^{(\prime)}$ in the
framework of perturbative QCD and evaluate analytically the one-loop integrals
with the light quark masses kept. Interestingly, the branching ratios
$\mathcal{B}(h_{c}\rightarrow\gamma\eta^{(\prime)})$ are insensitive to both
the light quark masses and the shapes of $\eta^{(\prime)}$ distribution
amplitudes. And it is noticed that the contribution of the gluonic content of
$\eta^{(\prime)}$ is almost equal to that of the quark-antiquark content of
$\eta^{(\prime)}$ in the radiative decays $h_{c} \rightarrow
\gamma\eta^{(\prime)}$. By employing the ratio
$R_{h_{c}}=\mathcal{B}(h_{c}\rightarrow\gamma\eta)/\mathcal{B}(h_{c}\rightarrow\gamma\eta^{\prime})$,
we extract the mixing angle $\phi=33.8^{\circ}\pm2.5^{\circ}$, which is in
clear disagreement with the Feldmann-Kroll-Stech result
$\phi=39.0^{\circ}\pm1.6^{\circ}$ extracted from the ratio $R_{J/\psi}$ with
nonperturbative matrix elements $\langle 0\mid
G^{a}_{\mu\nu}\tilde{G}^{a,\mu\nu}\mid\eta^{(\prime)}\rangle$, but in
consistent with $\phi=33.5^{\circ}\pm0.9^{\circ}$ extracted from the asymptotic
limit of the $\gamma^{\ast}\gamma-\eta^{\prime}$ transition form factor and
$\phi=33.9^{\circ}\pm0.6^{\circ}$ extracted from $R_{J/\psi}$ in perturbative
QCD. We also briefly discuss possible reasons for the difference in the
determinations of the mixing angle.
