The effects of water-saturation (WS) and water-loss (WL) on bank-slope became obvious over a period of time as reservoir water level fluctuated cyclically when the Three Gorges reservoir became operational in 2003. According to the natural processes of WS and WL during 2005-2009

purple soil samples were collected from the Shiliushubao landslide of Three Gorges to determine chemical and mineral compositions by full quantitative analysis of soil samples and mineral composition analysis of soil samples

and to observe microstructure of samples by soil samples electron microscopy. The impact of water-rock interaction on bank-slope soil and its mechanical law were analyzed during the processes of WS and WL. The study results show that the effects of WS and WL processes on the chemical and mineral compositions of soils from different elevations of the slope are different; soil from higher elevation (172 m) of landslide is impacted more heavily. After the WS and WL processes

the contents of SO2

Al2O3 and Na2O in soil increase while CaO and loss on ignition (LOI) in soil decrease. With the variations of chemical compositions contents

the microstructure of soil changes from dense plaque structure to random flocculation structure; and it is a huge impact on the mechanical effects of bank-slope.