  We investigate the jet-quenching parameter $\hat{q}$ for the quark-gluon
plasma (QGP) for $N_c=3$, defined nonperturbatively with the Wilson loop in the
light-cone (LC) coordinate, at finite temperature $(T)$. Considering the
effective static (heavy) quark-antiquark potential $V_{\bar{Q}Q}=\sigma
L+C-A/L$, where $L$ indicates the LC transverse separation between the quarks,
we obtain $\hat{q}\approx8V_{\bar{Q}Q}/L^2$. The $T$ dependences for $L$ and
other relevant parameters are extracted from the $T$-dependent instanton
(trivial-holonomy caloron) length parameters and the lattice QCD data. By
choosing $L\approx{a}\approx\bar{\rho}_T$, in which $a$ and $\bar{\rho}_T$
denote the lattice spacing and the $T$-dependent average (anti)instanton size,
respectively, we acquire numerically that $\hat{q}=(5\sim25)\,\mathrm{GeV/fm}$
for $T=(0\sim0.6)$ GeV, and these values are well consistent with other
estimations from AdS/CFT and experimental analyses. It turns out that $\hat{q}$
is produced almost by the Coulomb and constant potentials of $V_{\bar{Q}Q}$. We
also observe that the ratio $T^3/\hat{q}$ turns into being saturated to
$\sim4.45\times10^{-2}$ for $T\gtrsim0.4$ GeV, indicating the strongly-coupled
QGP, and $\hat{q}$ behaves proportionally to $T^3$ for high $T$.
