Abstract: In the framework of linear baroclinic primitive equations, calculation is undertaken for dispersion of inertia gravitational waves in different kinds of 3D (three-dimensional) grids from the perspective of frequency and group velocity, and the reason of the deviation in various grids is analyzed. The results indicate that such 3D structures as C/CP (horizontal grids with Arakawa C grids, and vertical with Charney-Phillips) and Z/LZ (horizontal grids with Z grids, and vertical with 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 models.