  We consider the nuclear shadowing in deep-inelastic scattering corresponding
to kinematic regions accessible by future experiments at electron-ion
colliders. The gluon distribution at small $x$ is obtained using an improved
dipole model depended on the impact parameter for atomic nucleus and compared
with nCETQ15 parametrization group. The nuclear shadowing at small $x$ is
defined within the color dipole formalism with respect to the mass number $A$.
Its behavior is predicted for light nuclei in a wide range of the impact
parameter $b$ and the transverse dipole size $r$. The nuclear saturation at
large-$r$ (small $\mu^2$) is observable. The behavior of the nuclear ratio
$\sigma^{A}_{\mathrm{dip}}/\sigma_{0}$ is similar to the
Golec-Biernat-W$\ddot{\mathrm{u}}$sthoff (GBW) model in a wide range of $r$ for
light and heavy nuclei at small $x$.
