  We investigate the observability of the top anomalous $tqZ$ couplings via the
trilepton signatures at the Large Hadron Collider~(LHC) with the center-of-mass
energy of 14 TeV. We focus on signals of the $tZ$ associated production with
the decay mode $t\to W^{+}b\to b\ell^{+}\nu_{\ell}$, $Z\to \ell^{+}\ell^{-}$,
and $t\bar{t}$ production with the decay mode $\bar{t}\to Z(\to
\ell^{+}\ell^{-})\bar{q}$ and $t\to b\ell^{+}\nu_{\ell}$, where $\ell=e, \mu$
and $q$ reflects up and charm quarks. It is shown that at $3\sigma$ level, the
FCNC top quark decay branching ratios can be probed at, respectively, about
$Br(t\to uZ) \leq 1.3\times 10^{-4}$ and $Br(t\to cZ) \leq 4.2\times 10^{-4}$
with the integrated luminosity of 100 fb$^{-1}$, and probed down to $Br(t\to
uZ) \leq 2.2\times 10^{-5}$ and $Br(t\to cZ) \leq 8\times 10^{-5}$ for the
high-luminosity LHC with 3000 fb$^{-1}$.
