In order to study the soil water movement characteristics of the slope collapse erosion, the author collected red soil from granitearea of collapse gully erosion in Hubei Tongcheng County and studied the preferential flow and impact factor. The collection of 1 kind of clay and 3 kinds of sand layer were loaded in transparent PVC soil box, 60 cm long, 11 cm wide, and 110 cm high, respectively, in accordance with the order of "sand under the red soil". Rainfall infiltration was simulated using three soil boxes in different initial moisture content (12.2%～23.6%) and rainfall (0.7,1.2 mm/min), and the instantaneous dynamic soil moisture of 20 positions of the soil mass was monitored by the time domain reflectometry (TDR) in high frequency. Thus, according to the spatio-temporal variations of the water content, the soil preferential flow characteristics were recognized. The results showed that the infiltration of precipitation was not uniform infiltration, and when the soil saturated hydraulic conductivity was larger and the path condition of marcropore was better, the preferential flow was more likely to occur, and its scope of influence was more extensive. The greater the rainfall intensity, the more obvious effect the preferential flow and the surrounding matrix, the greater the preferential flow rate. The rainfall intensity of 1.2 mm/min had a preferential flow rate 1.8～4.0 times of that by the rainfall intensity of with 0.7 mm/min. When the treatment of initial moisture content was smaller, the initial flow time was later and the flow rate was smaller. The results showed that the preferential flow was affected by precipitation and initial water content, but the effect of soil properties was greater.