We investigated the zero field splitting (ZFS) of a single iron (II) phthalocyanine (FePc) molecule on clean Cu(110) and Cu(110) (2×1)-O surfaces mainly by using inelastic electron tunneling spectroscopy (IETS) with STM. On the Cu(110) (2×1)-O surface, the excitations between the spin states were observed. Adsorption of FePc on the (2×1)-O surface reduces the symmetry of the ligand field for the Fe atom, resulting in the switching of the easy-magnetization direction from the easy-plane to easy-axis. On the clean Cu(110) surface, there is no signal relevant to the excitation. The spin state converts from triplet to singlet due to the stronger coupling with the surface as is confirmed by photoelectron spectroscopy. These findings demonstrate the importance of coupling at molecule-substrate interface for manipulating the magnetic properties of adsorbates.