  We calculated the next-to-leading order (NLO) QCD corrections to the cross
sections for direct top quark productions induced by model--independent flavour
changing neutral current couplings at hadron colliders. The NLO results
increase the experimental sensitivity to the anomalous couplings. Our results
show that the NLO QCD corrections enhance the leading order (LO) total cross
sections at the Tevatron Run 2 about 60% for both of $\kappa_{tc}^g$ and
$\kappa_{tu}^g$ couplings, and enhance the LO total cross sections at the LHC
about 40% for $\kappa_{tc}^g$ couplings and 50% for $\kappa_{tu}^g$ couplings,
respectively. Moreover, the NLO QCD corrections vastly reduce the dependence of
the total cross sections on the renormalization or factorization scale, which
leads to increased confidence in predictions based on these results.
