Abstract: The Qianjia granitoid pluton is a typical granitic complex in Hainan Island during the Late Cretaceous. The complex consists of three major rock types, i.e., granodiorite, monzogranite and syenogranite. The mineral assemblages commonly composed of biotite,hornblende, plagioclase, alkali feldspar, and quartz. To further reveal the processes of rock formation and the characteristics of their source regions, as well as to infer crust-mantle interactions, this paper selects the Qianjia pluton and utilizes electron microprobe to analyze major elements of major minerals in different rock types. The results show that hornblendes and biotites are likely originated from crust-mantle mixing, and annulus zoned plagioclase may represent a magmatic activity. Microscpic identification shows a large number of magma unbalanced structures occur in the Qianjia pluton, such as embedded crystal structure of plagioclases and hornblendes, and acicular apatites, These phenomena indicate a mixing process for generation of the Qianjia composite magma combines mineral assemblages and morphological characteristics of the enclaves. As a result, the petrological and mineralogical data indicate a crust-mantle mixing generation for the Qianjia granitic complex, the mineralogical data also shows similar characteristic to I-type granites with calc-alkaline magma source, biotites formed in a low oxygen fugacity environment.