Mineral constituents and their weathering in yellow-red soils derived from granite in middle and lower reaches of the Yangtze R iver were studied. Light minerals in fractions greater than silt contained over 80% quartz and feldspar, and heavy ones contained more than 60% various iron minerals and about 30% mica and hornblende. Kaolinite was the main clay mineral, the content of which was about 300 -400 g/ kg. Quartz was weathered very weakly, Ca-feldspar was weathered over 65%, and about 25% of Na-feldspar was weathered. The vermiculitisation of mica was relativly obvious, > 50% of mica being weathered to vermiculite. Weatherable minerals were also obviously weathered, the weathering being about 60%. Soil vermiculite was evolved through the process of mica→hydromica→vermiculite-chlorite→vermiculite, which was closely related to leaching situation and oxidic condition. Mineral constituents and their weathering in yellow-red soils derived from granite in middle and lower reaches of the Yangtze R iver were studied. Light minerals in fractions greater than silt contained over 80% quartz and feldspar, and heavy ones contained more than 60% various Kaolinite was the main clay mineral, the content of which was about 300-400 g / kg. Quartz was weathered very weakly, Ca-feldspar was weathered over 65%, and about 25% of iron content was about 30% mica and hornblende. The vermiculitis of mica was relativly obvious,> 50% of mica being weathered to vermiculite. Weatherable minerals were also obviously weathered, the weathering being about 60%. Soil vermiculite was evolved through the process of mica → hydromica → vermiculite-chlorite → vermiculite, which was closely related to leaching situation and oxidic condition.