  In this paper we are going to study a class of Schr\"odinger-Poisson system
$$ \left\{ \begin{array}{ll}
  - \Delta u + (\lambda a(x)+1)u+ \phi u = f(u) \mbox{ in } \,\,\,
\mathbb{R}^{3},\\ -\Delta \phi=u^2 \mbox{ in } \,\,\, \mathbb{R}^{3}.\\
\end{array} \right. $$ Assuming that the nonnegative function $a(x)$ has a
potential well $int (a^{-1}(\{0\}))$ consisting of $k$ disjoint components
$\Omega_1, \Omega_2, ....., \Omega_k$ and the nonlinearity $f(t)$ has a
subcritical growth, we are able to establish the existence of positive
multi-bump solutions by variational methods.
