Results of soil water content by sampling at 77 nodes of 10×l0m grid (Fig.1) in a flat experiment field of 66×100m² indicated that the distribution of soil moisture of upper layct (0-45 cm) was normal distribution.The moisture of subsoil (45-90cm) was abnormal distribution which could be due to a clayey layer.with high water capacity hurried there in different thickness The error estimates of the average moisture content of upper layer was 0.024(g/g) when 4 samples were taken.By the analysis of semivariance,it was shown that the spatial stribution of soil moisture was structural (Fig.3).Its correlation range (lag) was about 30m.This spatial structure was stable,which was also proved by the analysis of rank correlation.Therefore,when monitering the soil moisture flutuation,the experimental error would be disreased by choosing the sampling locations at which their moisture content are as close as possible to the average of total values and their distances are corresponding to the correlation range.