  We investigate the signature of a heavy charged Higgs boson of the Minimal
Supersymmetric Standard Model in the lepton plus multi-jet channel at the Large
Hadron Collider with four $b$-tags. The signal is the gluon-gluon fusion
process $gg\to t\bar b H^-$, followed by the $H^-\to \bar t b$ decay, while the
main background is from $gg\to t\bar t b\bar b$. We find that the two can be
separated effectively by kinematic cuts and mass reconstruction, but the signal
size is not very large in the end. Nonetheless, with a good $b$-tagging
efficiency, $\epsilon_b\sim50%$, this channel can provide a viable signature
over a limited but interesting range of the parameter space.
