Abstract: The processes of the proton transfer between 2-hydroxy pyridine (Hy) and 2(1H)-pyridone (Py) were investigated by using density functional theory of quantum chemistry method at B3LYP/6-31G(d) level. The four possible reaction pathways: (a) intramolecular proton transfer;(b) water-assisted intermolecular transfer; (c) isomerization by double-proton transfer in the dimer and (d) intermolecular proton transfer via the complex formed by Hy and Py were investigated in the present paper. The calculated results showed that the processes in (b),(c) and (d) has lower activation energies than that of the intramolecular tautomeric oxo-hydroxy reaction (a) because of the formation of hydrogen-bonded complexes in (b),(c) and (d).The activation energies corrected by scaled zero-point vibrational energies for the four reaction processes calculated at the B3LYP/6-31G(d) level are 137.2,38.7,2.6 and 17.3 kJ•mol－1,respectively.It is likely that the hydrogen bonds formed in the complexes play an important role in proton transfer processes in the later three reaction pathways.