Abstract: In this paper, soil moisture vertical variance was used to analyze the moisture characteristic of soil in yellow soil sloping field of Guizhou Province. First, wavelet transform method was used to check saltation points. Second, the response of the variance of soil moisture of each layer was explored through the analysis of mutual spectrum. Last, time lag was studied by phase frequency characteristic. The results indicated that the change of soil moisture in vertical direction was an approximate random stable signal process, and the breaking phenomenon of surface layers(0～20 cm) was more than underlayers(20～100 cm), time lag was demonstrated in the changes of soil moisture in most soil layers.