  Within the framework of Polyakov-Nambu-Jona-Lasinio model and by means of
Multiple Reflection Expansion, we study the finite volume effects on chiral
phase transition, especially its influence on the location of the possible
critical end point (CEP) and masses of mesons. Our result shows that as the
radius of spherical volume decreases, the location of CEP shifts toward smaller
temperature while changes little in chemical potential. As for the finite
volume effects on the masses of mesons, the masses of $\pi$ and $K$ increase
with decreasing volume, while for $\sigma$, $\eta$ and $\eta '$ the situation
is the opposite. Especially, the masses of chiral parters $\pi$ and $\sigma$
get closer as the volume decreases, indicating that the dynamical chiral
symmetry breaking effect reduces with decreasing volume.
