In the framework of linear baroclinic nonhydrostatic anelastic equations,calculation is undertaken for dispersions of inertia gravitational waves in different kinds of 3D(three-dimensional) grids from the perspective of frequency and group velocity, indicating that such 3D structures as EL/CP, C/CP and Z/LZ are superior to others in the computational dispersion properties, thereby providing a guidance to the selection of 3D grids applicable to atmospheric primitive equation nonhydrostatic models.