  We present numerical simulation of QCD with two dynamical quark flavors
described by the overlap fermion action on a $16^3\times 32\times (0.12 {\rm
fm})^4$ lattice. We calculate pseudo-scalar masses and decay constants and
investigate their chiral properties. We test the consistency of our data with
the two-loop chiral perturbation theory predictions, which should also be valid
at finite lattice spacings because of the exact chiral symmetry, including the
finite size effects.
