  The recent experimental results of LHCb collaboration suggested the existence
of pentaquark states with charmonium. To understand the structure of the
states, a dynamical calculation of 5-quark systems with quantum numbers
$IJ^P=\frac{1}{2}(\frac{1}{2})^\pm$, $\frac{1}{2}(\frac{3}{2})^\pm$ and
$\frac{1}{2}(\frac{5}{2})^\pm$ is performed in the framework of chiral quark
model with the help of gaussian expansion method. The results show that the
negative parity states can be bound states while all of the positive parity
states are the scattering states. The $P_c(4380)$ state is suggested to be the
bound state of $\Sigma^*_cD$. Although the energy of $\Sigma_cD^*$ is very
close to the mass of $P_c(4450)$, the inconsistent parity prevents the
assignment. The calculated distances between quarks confirm the molecular
nature of the states. Other five-quark bound states of the combination of
$\Sigma_cD$ and $\Sigma^*_cD^*$ are also found in the region about 4.3GeV and
4.5GeV.
