  Vector-like quarks are introduced in various new physics models beyond the
standard model (SM) at the TeV scale. We especially consider the case that the
quark is singlet (triplet) under the SU(2)$_L$ (SU(3)$_c$) gauge group and
couples only to the third generation quarks of the SM. The vector-like quark of
this kind is often called a top partner. The top partoner $t_p$ decays into
$bW, tZ$ and $th$. In the ATLAS and CMS collaborations, the top partner has
been searched in the final states of $bW$ and $tZ$, while the search based on
the decay mode $t_p\to th$ has not been started yet. However, the decay into
$th$ is important since it is significantly enhanced if some strong dynamics
exists in the TeV scale. In the presence of a light higgs boson, the decay mode
$t_p\to th$ followed by $h\to b\bar{b}$ produces three bottom quarks. We study
the sensitivity for the top partner using multi-b-jet events at the 8 TeV run
of the LHC experiment. The multi-b-jet eventss turn out to play a complementary
role to the existing $t_p\rightarrow bW$ and $tZ$ searches by the ATLAS and CMS
collaborations.
