Abstract: The Huayangchuan deposit in Shaanxi Province is located in the Xiaoqinling metallogenic belt in contact between the North China Craton and the Qinling orogenic belt. It is a world-class uranium and niobium polymetallic deposit related to carbonatite, in which pyrochlore is the major U and Nb-bearing mineral. Although the Huayangchuan metallogenic mechanism has been well studied, the magmatic-hydrothermal evolution process of the deposit and its relationship with mineralization were poorly understood. Hereby, this paper study mineralogy, chemical composition and evolution characteristics of two types of primary pyrochlore (pcl Ⅰ and pcl Ⅱ) and three types of altered pyrochlore (pcl Ⅰ alt1, pcl Ⅰ alt2 and pcl Ⅱ alt) in the Huayangchuan deposit. The results show uranium and niobium mineralization in Huayangchuan carbonatite is closely related to the Late Triassic magmatism. It was related to a mantle-derived, initially U-rich carbonatitic magma, which has been further enriched in U by crystallization differentiation and formed the primary (magmatic) pyrochlore (pcl I), primary pyrochlore (pcl Ⅱ) and primary uraninite (Ur1) through partial melting from the mantle. In the early Cretaceous, the carbonatite in Huayangchuan were subjected to high-temperature hydrothermal alteration, and part of Nb and U released from the early pyrochlore (pcl Ⅰ) were dissolved and reactivated by the high temperature high-F fluid, which formed the primary uranite (Ur2), the altered pyrochlore (pcl Ⅰ alt1) and the secondary titanite (Ttn2). The primary pyrochlore (pcl Ⅰ) and primary pyrochlore (pcl Ⅱ) can be replaced by the altered pyrochlore pcl Ⅰ alt2 and altered pyrochlore pcl Ⅱ alt in the post ore low-temperature alteration. These results indicate that two magmatic-hydrothermal uranium-niobium mineralization and one post-mineralization low-temperature hydrothermal alteration occurred in Huayangchuan deposit during late Triassic and early Cretaceous.