  We investigate symmetries of Witten-Dijkgraaf-E.Verlinde-H.Verlinde (WDVV)
equations proposed by Dubrovin from bi-hamiltonian point of view. These
symmetries can be viewed as canonical Miura transformations between genus-zero
bi-hamiltonian systems of hydrodynamic type. In particular,we show that the
moduli space of two-primary models under symmetries of WDVV can be
characterized by the polytropic exponent $h$. Furthermore, we also discuss the
transformation properties of free energy at genus-one level.
