A direct reaction pathway for water gas shift reaction (WGSR) in gas phase, H2O + CO -> H-2 + CO2, was discovered by using anharmonic downward distortion following method. The direct WGSR is accompanied by a roaming-like mechanism. To examine the initial conditions of the direct WGSR, we carried out ab initio molecular dynamics simulations and showed that cooperative excitations of OH-stretching vibrational modes and the orientational control of reactants are required for the direct WGSR.