The spatial heterogeneity of unsaturated zone and soil layer in watershed is the main source of non -linearity inhydrological process, and it is also the weakness in hydrological experiments, especially in its spatial distribution. Traditional studiesof description are usually related to the date counter map, which need to be improved. This paper analyzed the variationmechanism and spatial distribution variation of soil water δ18O at different depths by combining traditional statistical andgeostatistical methods, which can provide data basis for the application of geostatistical methods on the quantitative analysis ofspatial distribution of hydrological parameters. The results indicate that the spatial model of δ18O semi-variance model of soil watervaries dramatically from pure nugget model to Gauss and exponential model and then back to pure nugget model in 15 cm soillayer. Evaporative fractionation was used to estimate the evaporative intensity. The evaporative intensity varies with the depth, butthe 45 cm soil layer is the strongest (11%), and the standard deviation and deviation of the discrete properties are also thestrongest, which shows that the key role in the process of unsaturated zone is not the surface soil layer, but the middle soil layer.It is 45cm in the Shuiwenshan experimental watershed. The spatial variation of the δ18O in the 45 cm soil layer is relatively stable(Gauss model and exponential model), and the value of C0/(C0+C1) in Gauss model is close to zero, which also shows that thestronger spatial auto-correlation is formed with the flow of soil water after infiltration, evaporation and the fusion with original δ18Oin soil water. Participating in "migration" and "mixing" at 80 cm depth was the water δ18O in 46 days ago, and the change ofspatial auto-correlation presents obvious hysteresis, and spatial correlation appears 48 hours later. It shows that the classical andgeostatistical methods are effective in the spatial quantification of hydrological parameters. Meanwhile, there are some unexpectedphenomena in the hydrological mechanism, especially those contrary to the traditional concepts.