The Pingtan scheelite deposit is a newly-discovered Caledonian W deposit situated in the northwestern portion of the Miao’ershan granitic batholith in the Nanling Range. The W mineralization can be divided into three stages, the altered granite-scheelite stage (I), the quartz-scheelite stage (II) and the quartz-sulfide stage (III). This contribution characterizes the mechanisms of ore formation of the deposit using fluid inclusion microthermometry, H-O isotopes, and in situ S isotopes. Fluid inclusion microthermometry demonstrates that the scheelite mainly formed at moderate to high temperatures (∼260–380 °C for stage I and ∼ 240–300 °C for stage II). The inclusions were trapped at maximum pressures of ∼ 140 MPa, which corresponds to a maximum depth of ∼ 5.3 km. Homogenization temperatures of the inclusions decrease slightly from stage I to stage II mineralization, and more drastically from stage II to stage III, whereas their salinity decreases gradually during the entire mineralization process. Raman spectroscopy indicates that fluid inclusions in stages I and II contain CO₂, CH₄, and N₂, whereas those in stage III mainly contain H₂O. The presence of native bismuth, pyrrhotite, and marcasite, and the presence of CH₄-bearing fluid inclusions suggest reduced ore-forming conditions during Stages I and II. The δ³⁴S_CDT value (+0.8 to + 5.3 ‰, average 3.2 ‰) of sulfides and the δ¹⁸O_vsmow value of ore-bearing quartz, which decreases from Stage I (δ¹⁸O_vsmow = +5.1 to + 6.3 ‰) to Stage III (δ¹⁸O_vsmow = − 1.5 ‰ to + 0.6 ‰), as well as the presence of abundant fluid inclusions with daughter minerals in the first two stages, supports a magmatic origin for the ore-forming material, with exogenic fluid input after the tungsten mineralization stage. Based on the results of this contribution, boiling may be the dominant mechanism for the formation of W deposits in the Nanling Range.