  We present the complete calculations of the forward-backward asymmetry
($A_{\rm FB}$) and the total cross section of top quark pair production induced
by dimension-six four quark operators at the Tevatron up to
$\mathcal{O}(\as^2/\Lambda^2)$. Our results show that next-to-leading order
(NLO) QCD corrections can change $A_{\rm FB}$ and the total cross section by
about 10%. Moreover, NLO QCD corrections reduce the dependence of $A_{\rm FB}$
and total cross section on the renormalization and factorization scales
significantly. We also evaluate the total cross section and the charge
asymmetry ($A_{\rm C}$) induced by these operators at the Large Hadron Collider
(LHC) up to $\mathcal{O}(\as^2/\Lambda^2)$, for the parameter space allowed by
the Tevatron data. We find that the value of $A_{\rm C}$ induced by these
operators is much larger than SM prediction, and LHC has potential to discover
these NP effects when the measurement precision increases.
