Xiangshan caldera is located in the northwest of South China, Caledonian folded belt, which is elliptical and occurs on the basement of Sinian meta- morphic rocks. Because the violent volcanic activities in the Late Jurassic, especially the huge volume extrusion at higher speed in the late stage, the collapse arose when the transitional magma chamber was emptied. Subvolcanic coatis intruded along the collapsed ring faults. The volcanic complex is mainly composed of fragmentizing phenocrystic rhyolites. The volcanic activities began with the acid, with the highest in acidity in the middle-late stage and terminated with the marked decrease in acidity and alkalinity. The volcanic complex is principally composed of the acid vol- caaic and subvolcanic rocks. The potassium content is poor in them. The vol- panic complex belongs to calc-alkali, high-alumina, basalt series. The homogenization temperatures of glass inclusions in the phenocrysts of the volcanic rocks are equal to or above 1200℃.1t indicates that the magma was formed at higher temperature and at greater depth. The initial Sre87/Sr86 ratio of the volcanic complex is 0.7117士0.0009，reflecting the magma was the products that remelted in 'the middle and lower part of the sial and more mantle materials were mixed into the magma. Host rocks of uranium mineralization are rhyolite-dacite, fragmentizing phenocrystic rhyolite and subgranitic porphyry. The uranium abundances of various rocks in the volcanic complex are markedly less than that of granitic bodies in Southeastern China. 90 per cent of the uranium contains in the matrix according to the studies of uranium distribution. The uraninite is not preseat in the volcanic and subvolcanic rocks. The Sre87/Sr86 ratio of apatites associated with uranium minerals is very approximate to the initial Sre87/Sr86 ratio of the volcanic complex. It indicates that the source of uranium is derived from the depth.