The purpose of this paper is to determine the effects of elevation and lithology on clay mineral composition of soils derived from limestone in south China. The research areas were located in the Jinfo Mountain, Chongqing municipality, and the Huaihua Basin, Hunan Province, two karst regions. The samples of Black limestone soil (Jf07) and the Mountain yellow-brown earth (Jf12) were collected on the top of the Jinfo Mountain, about 2 000 m in elevation; the samples of Yellow limestone soils (Jf02, Jf20 and Jf23) on the mid- and lower-slopes of the Jinfo Mountain, about 600 ~ 1 200 m in elevation; the sample of Red limestone soil (Hh01) in the Huaihua Basin, Hunan Province, over 200 m in elevation. Soil mineralogy of the samples was determined by X-ray diffraction (XRD) on the <1 µm (clay) fraction in B horizons. Results show, in the mid-subtropical zone of China, clay minerals in the limestone soils are dominated mainly with 2:1-typed illite or vermiculite, in addition to some 1:1-typed kaolinite and halloysite. With elevation going downwards, the fractions of kaolinite and goethite in soils exhibit a trend of increase, and their crystallinity increase too; this shows that, with the locations descending on slope, the soils are intensifying in weathering. On top of the Jinfo Mountain, lithology, topographic feature and vegetation are important factors, affecting soil forming process and mineral composition of the clay. On top of the Jinfo Mountain, the Permian Maokou Formation is a set of stratum of limestone larded with grey-dark carbonaceous shale; the Permian Longtan Formation is a set of interbedded rocks of limestone and sandstone-shale. Due to being significantly affected by the Permian Maokou Formation, Jf07 soil is weak in weathering, its clay mineral composition is complicated; there are certain amounts of talc and aliettite, which are residues from its grey-dark parent rocks. But, Jf12 soil is well developed, its clay mineral composition is simple, and its main clay mineral is vermiculite; this is attributed to the impact of the parent rock (Permian Longtan Formation).