  We investigate the linear growth function for the large scale structures of
the universe considering modified Chaplygin gas as dark energy. Taking into
account observational growth data for a given range of redshift from the
Wiggle-Z measurements and rms mass fluctuations from Ly-$\alpha$ measurements
we numerically analyze cosmological models to constrain the parameters of the
MCG. The observational data of Hubble parameter with redshift ($Z$) is also
considered. The Wang-Steinhardt ansatz for growth index $\gamma$ and growth
function $f$ (defined as $f=\Omega_{m}^{\gamma} (a)$) are considered for the
numerical analysis. The best-fit values of the equation of state parameters
obtained here is employed to study the growth function $(f)$, growth index
($\gamma$) and state parameter ($\omega$) with redshift $z$. We note that MCG
satisfactorily accommodates an accelerating phase followed by a matter
dominated universe.
