  By presenting the mass-independent potentials of the Kaluza-Klein (KK) modes
in the corresponding Schr\"{o}dinger equations, we investigate the localization
and mass spectra of various bulk matter fields on an AdS thick brane. For a
spin 0 scalar $\Phi$ coupled with itself and the domain-wall-forming field
$\phi$ via a coupling potential
  $V=(\lambda \phi^{2}-u^{2})\Phi^{2}+\tau\Phi^{4}$, the localization and
spectrum are decided by a critical coupling constant $\lambda_{0}$. When
$\lambda>\lambda_0$, the potential of the scalar KK modes in the corresponding
Schr\"{o}dinger equation tends to infinite when far away from the brane, which
results in that there exist infinite discrete scalar bound KK states, and the
massless modes could be trapped on the AdS brane by fine-tuning of parameters.
When $\lambda<\lambda_0$, the potential of the scalar KK modes tends to
negative infinite when far away from the brane, hence there does not exist any
scalar bound KK state. For a spin 1 vector, the situation is same like the
scalar with a coupling constant $\lambda>\lambda_0$, but the zero mode can not
be localized on the brane. For a spin 1/2 fermion, we introduce the usual
Yukawa coupling $\eta\bar{\Psi}\phi\Psi$, and find that the localization of the
fermion is decided by a critical coupling constant $\eta_0$. For $\eta >
\eta_0$, the four-dimensional massless left chiral fermion and massive Dirac
fermions consisted of the pairs of coupled left-hand and right-hand KK modes
could be localized on the AdS brane, and the massive Dirac fermions have a set
of discrete mass spectrum. While for the case $0<\eta < \eta_{0}$, no
four-dimensional Dirac fermion can be localized on the AdS brane.
