Abstract：The newly discovered karst problem of marlite in Three Gorges region is an important problem in engineering geology. Marlite is of both the properties of limestone in which CaCO3 can be dissolved and mudstone in which mud component can be weathered，which brings about the variation of the rock contents and textures. With the variation，the indexes of mechanical property of the rocks，such as uniaxial compressive strength (Rc)，deformation modulus (Eb)，elastic modulus (Et)，wave velocity (Vp and Vs)，dynamic elastic modulus (Ed) and dynamic shear modulus (Gd) drop gradually，so that some rocks belong to relatively soft rock by national standard. The loose soil layers brought about by dissolution and weathering，with the increase of montmorillonite content (S)，enlargement of specific surface area (B)，high liquid limit (wl)，high plastic limit (wp)，high plastic index (Ip)，strong pro-water property，expansive property and low shear strength (c，j)，are easy to be slided and deformed. As the foundation of project for population resettlement，there may occur geo-hazards，such as landslide，collapse，debris flow，uneven subsidence，fissure and cave-in by dissolution and weathering. So it is necessary to use flexible ideas to treat the stability of the foundation，and the key measure to control the geo-hazards is to keep the foundation from saturation.
