Raster data plays an important roll in the spatial analysis.The different raster resolution will cause the deletion of the vector information and influence the spatial analysis precision by using pedological professional knowledge-based method.In this research, the JiangXi province Yujiang region 1：50000 soil maps will be used and analyzed for the relationship between the soil type area and the raster scale in the soil taxonomy.The results turn out that the best raster scale interval for every soil types area in the great group is 0.5km, in the subgroup is 0.2km, in the soil genus and soil local type is 0.1km.The research shows that the suitable raster scale will reduce the data-density and raise the precision.So it will be more effective and more scientific to use the soil spatial data than before.