  We study on-shell decays of light vector meson resonances $\rho$, $K^*$ and
$\phi$ in the framework of chiral constituent quark model using resummation
calculations. Such studies are necessary for showing that chiral dynamics works
well at this energy scale. The effective action is derived by proper vertex
method, where resummation of all orders of momentum expansion is accomplished.
The loop effects of pseudoscalar meson are also taken into account, which play
an important role at this energy scale. The numerical results agree well with
the experimental data. A new method to explore the Chiral Symmetry
Spontaneously Breaking (CSSB) is proposed. It is found that the unitarity of
the effective meson theory resulted from resummation derivations demands an
upper-limit to the momentum of vector meson. This upper-limit, being critical
point, is just the energy scale of CSSB, and is found to be flavor-dependent.
