Analytical mode matching is an efficient method to calculate the diffraction of subwavelength grating. For stacked subwavelength gratings, the tangential component of an electromagnetic field is continuous at the boundary of adjacent different dielectric layers, and the contribution of each waveguide mode of the electromagnetic field in each layer to the electromagnetic field in the layer is equal to that of the tangential component of the electromagnetic field in the adjacent layer. The modes between adjacent layers are matched. Thus, the analytical mode matching can be applied to stacked subwavelength dielectric gratings. The diffraction efficiencies and the electromagnetic field distributions calculated using the analytical mode matching and the rigorous coupled wave analysis method are compared in this study. Comparison results show that the proposed analytical mode matching is an effective method for calculating the diffraction of stacked subwavelength dielectric gratings owing to its unique advantage in convergence and calculation speed and it offers a profound understanding of the diffraction effects of stacked subwavelength gratings on electromagnetic waves. The proposed method combined with optimization methods can be used to design new stacked subwavelength gratings and metasurfaces.