A groundwater-fluctuating region is a region where the groundwater varies sharply in water table and radiation range. With the aid of the geostatistics theory and GIS technology,study was carried out of a groundwater-fluctuating region in the lower reaches of the Heihe River. Based on the data collected from 64 sampling sites,Cross-Validation method and geostatistics method were adopted to select optimum interpolation method and fitted theoretic semivariogram models. Results show 1)spatial heterogeneity of soil salinity was very obviously in the groundwater-fluctuating region of the lower reaches of the Heihe River. That is,salt content in the soil increased gradually along the direction of the flowing water in the area. And the salt content should decrease gradually with the increasing vertical distance from the trunk course of the river,which was controlled by ground-water,but the decrease was replaced by regional variation. The regional variation was more distinct in the radiation range of East River than West Riverπs,which related to the source of replenishment of two rivers and chemical properties of the water;and 2)the range of variation is a measure of spatial heterogeneity. Based on the active variation ranges of the salt elements,7 km is supposed to be the maximum sampling scale in the study. This study is aimed at providing theoretic basis for regional ecological restoration,vegetation re-establishment,and rational arrangement of sampling sites in related studies.