  With the recent investigations of $g^{\ast}g^{\ast}-\eta^{(\prime)}$
transition form factor and $\eta-\eta^{\prime}$ mixing scheme, we present an
updated study of the radiative decays $J/\Psi\to\eta^{(\prime)}\gamma$ in
perturbative QCD. The decays are taken as a test ground for the
$g^{\ast}g^{\ast}-\eta^{(\prime)}$ transition form factors and the
$\eta-\eta^{\prime}$ mixing scheme. The form factors are found to be working
for glunic $\eta^{(\prime)}$ productions and the mixing angle is constrained to
be $\phi=35.1^{\circ}\pm0.8^{\circ}$.
