Terrain characteristics can be accurately represented in spectrum space. Terrain spectra can quantitatively reflect the effect of topographic dynamic forcing on the atmosphere. The one-dimensional weighted-average spatial spectral analysis method is used to explore the distribution characteristics of terrain and precipitation in Sichuan.The distribution of terrain height variance with wavelength is important for determining the required horizontal grid spacing for weather forecast models. The spectral analysis of terrain height variance gives an idea about the dominant wavelengths of terrain variance, which are used to specify the horizontal grid spacing required to resolve topographic perturbations. After fitting between the terrain height spectra and the wavelength, the fitting slope is associated with grid-size selection for weather forecast models.