The gas-phase proton-transfer reaction O- + HF --> OH(v = 0,1) + F- has been studied with the ab initio MO method and quasiclassical trajectory calculations. A strongly bound intermediate complex [OHF](-) is found on the ground-state potential energy surface (PES) obtained by the ab initio MO method. The intermediate complex is most stable at the collinear form. Three-dimensional quasiclassical trajectory calculations are performed with ab initio fitted PESs. The results show that the enhanced collision energy from 1.198 to 4.10 kcal/mol increases the product OH(v = 1) fractional population, P(v = 1) = {OH(v = 1)l[OM(v = 0) + OH(v 1)]}. The theoretical result suggests that this increase is due to the energy transfer from the translational mode to the vibrational mode of O-H in the deeper intermediate complex region. The trajectory calculations show that P(v = 1) at a collision energy of 5.31 kcal/mol is slightly smaller than that of 4.10 kcal/mol. These results are in reasonable agreement with experimental features derived by Leone and co-workers [J. Chem. Phys. 1992, 96, 298]. On the basis of the theoretical calculations, we propose a reaction model composed of two reaction channels : one is an intermediate complex channel model in which the reaction proceeds via a long-lived intermediate complex, [OHF](-), and the other is a direct channel model in which the reaction proceeds directly without the long-lived complex. The direct channel gives the vibrationally excited OH(v = 1, J = 0) radical, whereas the complex channel leads to the vibrationally ground and rotationally excited OH(v = 0, J = J’) radical.