Using the loess hillslope model and the artificial simulated rainfall experiment, morphological development of rill and the quantitative characteristics of morphological parameters were analyzed quantitatively under the rainfall intensities of 45, 87, and 127mm/h. The results showed that the quantitative morphological parameters of rill was not a single increase or decrease with the rainfall intensity increase, it presented the volatility changes with soil erosion development. Bare ground 1 and bare ground 2 showed different trends of change because of their different soil volume weight. A good relationship between the rill length and density and the fractal dimension of rill showed that the non-linear quantization parameter was not independent with the traditional one-factor quantization parameters. The fractal dimension as a quantitative parameter, can better reflect the change of rill length and density.