It is of great significance to dynamically simulate development and evolution of soil erosion for the purpose of erosion forecast. Traditionally, most soil erosion models are basically steady-state models that have limitations in real-time simulation of initiation and development of soil erosion. Cellular Automata (CA), with a "from bottom to top" dynamic modeling framework, is capable of simulating spatial-temporal evolutionary processes of the complex geographical system. So, in this paper, rill erosion on loess slope was studied. By means of artificial simulated rainfall and three dimensional laser scanning, how rill erosion started, developed and evolved on a loess slope,15o in gradient, under three intermittent artificial rainfall events were investigated and visualized in graphics. At the same time, the CA-Rill model, already available for simulation of rill erosion process, was used in couple with the NetLogo software, to analyze and compare results of the experiment and the results of model simulation. Results show: (1) The scanning images of the rill erosion processes under the three events of rainfall reveal that the entire course of rill erosion consisted of the following phases in sequence, splash erosion, sheet erosion, drop pit, intermittent rill, continuous rill and rill collapse. Rills developed very rapidly in length, and relatively slowly in width and depth, and soon connected with each other to form a rill network. At the end of the third rainfall event, erosion intensity reached as high as 22.107 kg m^-2, 22.04 times that at the initial stage of rainfall. (2) Results of the CA-Rill simulation indicate that in visualizing evolution of the rill erosion, the model could quite perfectly simulate the entire morphological development of rills and realize visualization of the simulation. (3) Validation of parameter t of the simulated rill erosion under three artificial rainfall events demonstrates that the simulation of mean rill depth of the longest rill, depth of the deepest rill and mean width of the longest rill is not so ideal. However, the effect of the simulation of horizontal rill intensity, length of the longest rill and erosion intensity is quite good.