In order to find out the effect of atomic motion on the population inversion of two atoms, the atomic states were analyzed by the method of quantum mechanics. It was found that the population inversion of two atoms was related to the field mode structure in an optical resonant cavity when the atoms were moving and the optical field was in coherent state. When two atoms in the cavity were fixed at initial time, the evolvement of population inversion of two atoms was periodic in the case of a small average photo number, and there were collapses and revivals of atomic inversion in the case of a large average photo number. The evolvement of population inversion of two atoms became well-regulated orderly under the coherent cavity field when atoms were in motion at initial time. The population inversion of two atoms will evolve in different periods when the two atoms move in axial direction at different velocity. The period of population inversion is the lease common multiple of periods of coupling coefficients between two atoms and field. When there are more average photon number in the cavity, the oscillation of population inversion will be faster. So it is possible to control the population inversion by properly choosing the velocity of atoms and the initial field.