  We derive the general 5-dimension metric structure of the $Dp-Dq$ system in
type II superstring theory, and demonstrate the physical meaning of the
parameters characterizing the 5-dimension metric structure of the
\textit{holographic} QCD model by relating them to the parameters describing
Regge trajectories. By matching the spectra of vector mesons $\rho_1$ with
deformed $Dp-Dq$ soft-wall model, we find that the spectra of vector mesons
$\rho_1$ can be described very well in the soft-wall $D3-Dq$ model, i.e,
$AdS_5$ soft-wall model. We then investigate how well the $AdS_5$ soft-wall
model can describe the Regge trajectory of axial-vector mesons $a_1$. We find
that the constant component of the 5-dimension mass square of axial-vector
mesons plays an efficient role to realize the chiral symmetry breaking in the
vacuum, and a small negative $z^4$ correction in the 5-dimension mass square is
helpful to realize the chiral symmetry restoration in high excitation states.
