Soil detachment process provides material for soil erosion, which is importance for understanding soil erosion process and building soil erosion model. In this study, the Brown soil was selected as the research object. Six soil moisture contents (3%, 6%, 9%, 12%, 15% and 18%), three slope gradients (5°, 10° and 15°), and three flow discharges (8, 12 and 16 L/min) were designed. The effects of soil moisture content, slope gradient and flow discharge on soil detachment capacity were explored. The results showed that: (1) As soil moisture content increased, soil detachment capacity decreased, and the differences of soil detachment capacity decreased; the detachment capacity was almost 0, when soil moisture content was 18%. There was a quadratic polynomial function between soil detachment capacity and soil moisture content, and soil detachment capacity was the highest when soil moisture content was 3%. (2) Soil detachment capacity increased with increasing of slope gradient when soil moisture content were 6%, 9%, 12% and 18%,respectively, and a quadratic polynomial relationship exsited between soil detachment capacity and slope gradient. When the slope gradient was 15°, soil detachment capacity reached the maximum. (3) Soil detachment capacity increased with increasing of flow discharge when soil moisture content was 3%~12%, and had a quadratic polynomial relationship with flow discharge. When flow discharge was 16 L/min, soil detachment capacity had the maximum value. (4) If only considered the influence of two factors, the contribution rate of the error was the largest. With three factors included, the contribution rate of slope gradient to the variation of soil detachment capacity was the largest (29.64%), followed by soil moisture content (22.29%) and flow discharge (19.72%). The simulation accuracy of soil detachment capacity could be increased from 0.550, 0.638 and 0.498 to 0.995 by including soil moisture content, flow discharge and slope gradient.