A new theoretical result of the total charge transfer cross section in collisions of O+ ion in the ground state with H-2 molecule is reported. The collision energy of the incident O+(S-4) ion ranges from 1 eV/u to 10 keV/u, covering the available experimental data. States of (4)A(2) and B-4(1) symmetry are included in the calculation. The state-resolved cross sections are obtained by using both the semiclassical and full quantum molecular orbital close coupling method. Based on our results, we propose a possible explanation for the large discrepancies in recent measurements among various experimental groups. (C) 2003 American Institute of Physics.