Abstract: Tungsten-tin mineralizations in the Nanling Range are closely related to granitic magmatism. Ability of controlling the mineralization of granites (or ore-forming potential of granites) is simply revealed by (1) the sources of granites (or initianl W-Sn enrichment); (2) differentiation degree of granites; and (3) nature and activity of fluids during granite evolution. This work aims to preliminarily establish a research system of ore-forming mineralogy for tungsten-tin granites in the Nanling Range. Biotite,titanite, cassiterite, rutile, wolframite, scheelite and wolframoixiolite are essentially useful minerals in clarifying the ore-forming potential of granites. On the crystal-chemical basis, these minerals are separately discussed by their petrographic, internal textural and chemical features. Criteria of these minerals as indicators of pricinple granite-related processes are presented for initial W-Sn enrichment in granites, crystallization of granite and hydrothermal mobility of ore-forming metals in late stage of granite differentiation. Features of ore-forming minerals are compared among three types of Nanling W-Sn granites (metaluminous tin granites, peraluminous tin granites and peralumnious tungsten granites). Finally, a case study was made in the Qitianling granite complex, which is essentially composed of the Sn granites of Furong and Cailing, and the Xintianling W granite. The Sn granites are characterized by biotite and titanite as Sn-bearing minerals, which suffured hydrothermal alteration, leading to tin leaching and subsequent crystallization of cassiterite. However, the Xintianling granite contains magmatic scheelite and wolframite. The mineralogical system of W-Sn granites helps to deepen metallogenic study and exploration of W-Sn deposits, and will be improved and perfected during the further researches.