Abstarct: Topography as a soil forming factor, cause variation on physical, chemical and mineralogical characteristics of soils. This variations also affected soil fertility. The soils of Mohammad Abad plain in Fars province were studied with respect to the influence of topography, as a soil forming factor, on genesis, morphology and mineralogy characteristics of soils. Mohammad Abad plain area is about 3500 ha. It's average rainfall is 488.3 mm and the average annual temperature is 13.1◦C.The soil temperature regime is Mesic and it's moisture regime is Xeric.Field studies, including excavation and descxription of the necessary profiles were carried out and the results laboratory analysis of soil samples were studied. The soil units were classified according to soil TAXONOMY and FAO systems. The soils genesis evolution are influenced due to topographical variation, surface runoff, rate of water infiltration into the soil and vertical transfer of salts and materials into the soil profile, and all these factors cause distinction of the soils which can be classified in three orders such as Alfisols, Entisols and Inceptisols. X-ray diffractograms of clay fractions of representative soils showed more or less similar clay minerals but with different proportions.Clay mineral studies showed the presence of Chlorite, Illite, Kaolinite, Smectite, Palygorskite and Quartz minerals.