  We study the confinement/deconfinement phase transition of holographic
AdS/QCD models by using Ricci flat $AdS_5$ black holes up to ${\cal
O}(\alpha'^3)$, which corresponds to the $\lambda$ expansion correction in the
dual field theory to $\lambda^{-3/2}$, where $\lambda$ is the 't Hooft coupling
constant. We consider two cases: one is the hard-wall AdS/QCD model where a
small radius region of the $AdS_5$ is removed; the other is the case where one
of spatial coordinates for the $AdS_5$ space is compactified, resulting in
Witten's QCD model in 2+1 dimensions. We find that in the hard-wall AdS/QCD
model, the deconfinement temperature decreases when the $\lambda$ expansion
corrections are taken into account, while in Witten's QCD model, the
deconfinement transition always happens when the ratio of inverse temperature
$\beta$ to the period $\beta_s$ of the compactified coordinate decreases to
one, $\beta/\beta_s=1$, the same as the case without the ${\cal O}(\alpha'^3)$
correction.
