Abstract: Liang-mao slope system is in the loess hilly and gully region. Its accumulated runoff and sediment production has a direct and significant impact on the slope erosion and the channel erosion below the margin line is the origination of headwater erosion and water flow under the act of heavy intensity rainfalls. In this research, we used an advanced research techniques: the three-dimensional reconstruction technology, and intermittent artificial rainfall simulation combining with soil erosion, as well as the theory of river sediment transport to express the erosion processes of slope varying from 5° to 35°. Evolving morphological parameters were used to elucidate hillslope erosion evolutionary rules and specific characteristics quantitatively. In combination with PhotoScan software and ArcGIS, the complex evolution process of soil erosion on variable gradient slope was graphed and digitalized, the evolution characteristics of morphology parameters and the relationship between detachment and morphological indicators were revealed qualitatively and quantitatively. The results showed that the evolution process of rill erosion on the loess liang-mao slope mainly experienced through four stages: The first stage was that the evolution stage from sheet erosion to rill erosion, which was often at a distance at the top of the slope had a series of eroded drop pits with the shape of beadlike and nearly equal spacing at different distances. The width of eroded pits was about 5-9 cm, the depth was about 1-4 cm with an average of 2 cm. The second stage was rill erosion development stage. In this stage, the micro rills were produced from drop pits under the interaction between water scouring and rain drops beating to the slope surface, the maximum length, width, depth and rill density of rills increased to 266, 7.6, 13.8 cm respectively. The third stage was the rill network stage in which bifurcating and merging of rills gradually formed rill network. The last stage was undercutting erosion of rills and widening of the trench walls causing rill network developing in length and depth, and finally, the micro gully erosion presented in the varied gradient slope surface. The maximum depth, length and width of rills and rill density were introduced to quantify development characteristic of rill networks and reflect the erosion intensity in vertical and horizontal direction, they all augmented with the increase of erosion amount. The hillslope gradually developed from flat to complex terrain. The results also showed that the eroded soil amount could be obtained through the value of DEM(digital elevation model) based on 3D reconstruction method before and after the rainfall runoff erosion process followed by, comparison with the actual measured subsurface rainfall erosion amount. The calculation showed that the deviation between the calculated erosion amount and the actual sediment production amount was only 20.82% at the first test, and the results of other tests varied around10%. Therefore, the technology was accurate enough to be applied in this study. The study not only can deepen people's understanding of the qualitative and quantitative process of soil erosion development, but also have profound academic value and practical guidance value for innovative erosion process research methods and guiding slope and gully treatment guidelines.