The Xintianling deposit is one of the largest skarn-type scheelite deposit in China. Recent discoveries of quartz vein-type scheelite mineralization within the deposit have raised questions about its origin and the evolution of ore-forming fluids, hindering a comprehensive understanding of the ore-forming process. We investigate the microtextures, trace elements, and oxygen isotope compositions of scheelite from different stages in both skarn-type and quartz vein-type W mineralizations. Combined with apatite geochemistry and U–Pb dating, we determine the timing of quartz vein-type mineralization and the evolution of hydrothermal system. Based on detailed petrological observation, three types (seven subtypes) of scheelite and two types of apatite are identified. The Mo contents and Eu/Eu* ratios of scheelite, along with the Ce/Ce* ratios of apatite indicate the oxygen fugacity of fluids during the skarn metallogenic episode is generally higher than that during the quartz-vein metallogenic episode. Furthermore, the Y/Ho ratios and REE patterns of scheelite indicate the presence of at least three significant episodes of fluid influx and fluid-rock interactions throughout entire ore-forming process. The O isotope compositions of Sch C in the quartz vein-type metallogenic episode reveal that the ore-forming fluids originated from a magmatic source, and meteoric water was mixed into the system, leading to the precipitation of Sch C4. The Ap I and Ap II closely coexists with scheelite, from quartz-vein metallogenic episode yield consistent U–Pb ages within error of 160.4 ± 2.4 Ma and 158.4 ± 1.3 Ma, respectively, indicating a close genetic link between quartz vein-type W mineralization and the fine-grained porphyritic biotite granite. Our study highlights the significance of pulsed fluid exsolution and the combined effects of multiple mechanisms, including fluid-rock interaction, fluid mixing, and changes in physicochemical conditions, in the formation of large W deposits.