  To obtain the value of electromagnetic coupling constant at $q^2=m^2_Z$,
$\bar{\alpha}$, which plays a key role in electroweak physics one has to
integrate the cross-section of $e^+e^-$-annihilation into hadrons divided by
$(s-m^2_Z)$ over $s$ from threshold to infinity. By combining, for each flavor
channel, the contribution of lowest resonance with the perturbative QCD
continuum, we obtain $1/\bar{\alpha} = 128.90\pm 0.06 $ a result which is close
to known result obtained with purely experimental inputs, i.e. $1/\bar{\alpha}
= 128.87\pm 0.12$.
