Marls frequently are considered as a part of sedimentary rocks that have been formed in low shallow and evaporated environments. Marls are mixture of clay (25-60%) and lime (40-70%). Geotechnical specifications of marls have been controlled by clay's parts. Modification of marls because of variation of moisture is one of the important problems that engineers are meeting. Although most of the landslides remind stable, in case of dry, they are unstable in case of increasing the moistures rainfall. In present research, based on the results of field survey and geotechnical tests, the effect of marl on foothill instability in road kuh_mond–khurmouj was characterized. The sequences of sedimentary rocks in the line of road are formed of clastic conglomerates of Bakhtiari formation and red& gray marls of Mishan, Aghajari and Gachsaran formation. Uniaxial strength and dry density of gray and red marls in study area is 50, 30 Kg/Cm2 and 20, 22 gr/Cm3 respectively. Physical and mechanical specification of marls demonstrate that they have high strength in dry conditions, hence they are able to keep foothills stable conditions in the height of 20 meters and 90 0 degree. Making use of Japan Road Corporation (J.R.C), the track of road from the viewpoint of slipping& failure is classified (A, B& C). The results showed that 65% from length of road is classed A on account of presence of marls at the side of road. Finally, after the recognition of the main factor, instability of slops in the line of roads, suitable solutions concerning instability of landslides are presented.