Jiuhuashan K-feldspar granite is a calcium_low granite body characterized by rich alkali-siliceous components and poor basic constituents. With oxidation degree somethat high,aluminium index colse to 1, and K2O approximately equivalent to Na2O, the granite should be of I-type. Nevertheless, its biotite is siderophyllite, and its initial87Sr/86Sr ratios are nonuniform and a bit higher (>0.707). These characteristics are not so consistent with features of I-type granaite. Consideridng Rb-Ba-Sr fractionation character and intense deficiency of MREE and using trace element web diagram, the author has revealed the intense magmatic crystallization and differentiation process and pointed out that this process had to do with the compositional variation of biotite and the obvious increase of strontium isotopes.The source materials of Jiuhuashan granite body were probably derived from middle and lower crust (εNd=-4.9~-6.6). Having experienced long unstable crystallization differentiation, the magmatic chamber eventually produced acid oversaturated magma, whose emplacement together with the early-mplaced Qingyang granodiorite body formed a complex batholith.