Quantifying differential erosion include selecting multi-lithological slopes and investigating the abilities to resist weathering and erosion for every lithology that interbeds with each other. This research first confirms potential bi-lithological slope cases and collects the environmental data of their vicinity. Related researches were studied and investigated for further discussion on the mechanism, phenomena, frequency and scale of differential erosion induced collapse. A sedimentary slope was carefully zoned after lithology based on detailed geological investigation. Two zones of the slope contain the interbeds of sandstone and shale, with thickness ratio equal to 4:1–8:1 and 2:1–1:1 correspondingly, sandstone to shale. Artificial weathering experiments take temperature and humidity as variables for a maximum 80 day-report ratios to be between weathering resistance of the sandstone to shale as 4.8. A numerical simulation of the case slope revealed that the amount and frequency of the continuous collapse induced by differential erosion was controlled by a joint set that is almost parallel to the slope face, and that the failure modes involves plane sliding, wedge sliding and toppling. Erosion of the shale layers produces overhanging sandstone blocks, and as the erosion amount goes beyond the centroids of potentially unstable sandstone blocks or clears out the obstruct in front of the sliding direction of a sandstone wedge, failure occurs.