Indoor rain simulation experiments were conducted in this study under different slope degrees (10°,15°,20°,25°),rainfall intensities (90,120 mm/ h) and slope lengths(5,7 m). The variation characteristics of fractal dimension of eroded soil particle composition under different rainfall conditions were analyzed. Results showed that the fractal dimension of soil particles was significantly positively correlated with clay and silt content of soil. There was a significantly negative correlation between fractal dimension and sand content of soil. The fractal dimension decreased as rainfall intensity increased, and the effects of slope degree and length were not obvious. Under the condition of 5 m slope length, fractal dimension showed the tendency of first declining then rising with rainfall duration. Under the condition of 7 m slope length, fractal dimension increased with rainfall duration under 20°and 25°slope conditions, while there was no obvious changing regulation under 10°and 15°slope conditions. The fractal dimension after rill appeared was lower than that before rill appeared under the 10°slope condition, significantly higher than that before rill appeared under 15°, 20°and 25°conditions.