A series of flume experiments were conducted at the condition of different runoff discharge, slope gradient and slope length. The Purple soil with a clay texture is the typical soil in the upper reaches of the Yangtze river.The flume with the size of 30 cm wide and 10 m long were used.eleven slope lengths including 0.5 m, 1 m, 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 9 m and 10 m were used. The flume were divided into 3 rills and the rill width is 10 cm. Three slope gradients including 5°,15° and 23°and three flow discharges with 5 L/min, 15 L/min, 25 L/min were used in the experiments. All experiments were repeated three times and there were total 297 test sessions. The results showed that rill erosion was affected by flow hydraulic characteristics, soil properties and slope characteristics, with the increase of flow sediment concentration, the rill erosion rate showed a trend of decrease; The greater the flow rate and slope gradient, the bigger rill flow detachment and the rill erosion rate. Under the condition of 5 l/min of small flow discharge, rill erosion rate restricted by detachment rate and had no strict linear relationship with sediment concentration, but under condition of 15 l/min, 25 l/min, rill erosion rate was linear correlation with sediment concentration. At the beginning of the rill, the rill erosion rate is the biggest, with the increases of rill length, the flow energy consumption for sediment transport, so sediment detachment decreased rapidly. The rill erosion rate and the rill length had a exponentially decreasing relationship by correlation analysis, and the correlation coefficient R2 changed between 0.45 to 0.98. By regression analysis, the average purple soil erodibility was 0.005 3 s/m, and the average critical shear stress was 2.92 Pa under experimental condition. The results provide data support for establishment and application of distributed physical model and serve as the further research of slope soil erosion of purple soil.