Abstract: This paper explores the complex relationship between the surface moisture of the loess high-filling body and provides the basis for preventing and controlling the shallow water-soil disasters of the slope. It takes a loess high-filling body in Ansai of Yan'an as the object, and carries out the in-situ long time series monitoring. The correlationship between the surface moisture of the loess high-filling slope under the influence of slope effect is studied by cross wavelet and wavelet coherence analysis method. The results show that the wavelet analysis method can be used to semi-quantitatively study the relationship between internal and external soil moisture in loess high-filling slope, can clearly show the relationship and variation details of two time series in time domain and frequency domain. There are two main resonance time scales of 0.06~1.78d and 3.56~28.47d between rainfall and shallow soil moisture of slope. The correlation shows an increasing trend in this two time scales. The correlation between rainfall and shallow soil moisture has obvious time scale dependence. The correlation between the soil moisture and the intensity of exchange and transformation can be expressed by the percent area of significant coherence(PASC). The average values of PASC at different positions of the slope as ranked as follows: the top of the slope(36.39%) < the upper slope(37.6%) < the middle slope(39.17%). The slope improves the exchange and transformation of vertical soil moisture. The existence of slope effect is not conducive to the transformation from rainfall to soil moisture, but enhances the exchange and transformation of surface vertical soil moisture.