Abstract: The equation of infrasonic wave taking into account the gravitational effect in moving media is derived, with multi-layer atmospheric model. The equations of frequency dispersion are specified by divergence of velocity, using a multi-layer atmospheric model. The dispersion characteristic of acoustic-gravity wave is evaluated. Numerical results have shown that both the phase and group velocities are of two kinds, the acoustical and gravitational. The dispersion of the acoustical velocities are more sensitive to wind. Usually the short period group velocity in downwind can differ as large as 10% from that in upwind. In some atmospheric model, the gravitational velocities are again divided to several groups, with different dispersion characteristics. The new results of infrasonic dispersion characteristics agree well with the observations from the nuclear explosion.