The minimum sampling areas (MSA) for the shrub communities in arid valleys in the upper reach of the Minjiang River were studied by fitting community species-area relationships using 3 types equations. The MSAs were determined at the proportional factor (ρ) 0.6, 0.7, 0.8 and 0.9. The proportional factors represent the proportion of the number of species within a sampling plot in total number of species. All the MSAs of the shrub communities at different elevation and slope face for the ρ at 0.6, 0.7 and 0.8 were somewhere around 100m². Hence the MSAs could be set as 100m²(10m×10m) at 60%～80% precision level. For the ρ at 0.9, i.e. for 90% precision level, the MSAs were less than 200m²(10m×20m). The MSAs and species richness increased gradually with the rising of altitude. At elevation below 2000 m, the MSAs and species richness on north facing slope were larger than south facing slope. However at the elevation around 2200 m, there was no difference among different facing slopes. For the shrub communities in arid valley in the upper reach of the Minjiang River, the species-area curve by fitting the first two equations are better than that by the third equation.