  The first order self-energy corrections of the kaon in the symmetric nuclear
matter are calculated from kaon-nucleon scattering matrix elements using a
chiral Lagrangian within the framework of relativistic mean field
approximation. It shows that the effective mass and the potential of K^+ meson
are identical with those of K^- meson in the nuclear matter, respectively. The
effective mass of the kaon in the nuclear matter decreases with the nuclear
density increasing, and is not relevant to the kaon-nucleon Sigma term. The
kaon-nucleus potential is positive and increases with the nuclear density.
Moreover, the influence of the resonance $\Lambda(1405)$ on the $K^-$-nucleus
potential due to the re-scattering term is discussed. Our results indicate the
K^- meson could not be bound in the nuclei even if the contribution of
$\Lambda(1405)$ resonance is considered.
