The Jiajika rare metal deposit is the largest pegmatit- type lithium deposit in Asia, and the No.308 pegmatite is the largest dyke exposed in the area. The No.308 pegmatite is characterized by well zonation (Ⅰ: fine grained muscovite- albite quartz zone; Ⅱ: medium- coarse grained albite- quartz- microcline zone; Ⅲ: medium grained tourmaline- albite- quartz zone; Ⅳ: medium grained spodumene- albite- quartz zone; Ⅴ: medium- fine grained spodumene- albite- quartz zone) and abundant rare- element minerals (including spodumene, beryl, cassiterite and columbite group minerals), thus can be used as an ideal object for our systematic study of the evolution history and diagenesis and mineralization mechanism of pegmatites. At present, the mineralogical study of the No.308 pegmatite is relatively rare, the magmatic- hydrothermal evolution and the characteristic of the initial melt and exsolved fluids of the pegmatite are poorly understood. The process of and influencing factors on the enrichment of rare- elements are still unclear. In this paper, we present EPMA results of mica, apatite, spodumene and tourmaline on their occurrence, textural features and chemical composition variations. The results show that: ① occurence of tourmaline minerals (~5 %) in zone Ⅰ (high temperature crystallization) of No.308 pegmatite indicates that the initial melt of the pegmatite is rich in B (>2 %); The large amount of spodumene in the Ⅳ and Ⅴ zones shows that the initial melt might be rich in Li; The contents of the main F- bearing minerals (tourmaline, apatite and mica) are relatively low, and the F concentrations of primary fluorapatites are relatively low (<3%), additionally, the lepidolite which can only be formed in F- rich environment is also very rare. These characteristics indicate that the initial melt of the No.308 pegmatite is likely to have low F content. ② Textural zone Ⅴ probably entered the magmatic- hydrothermal stage in the evolution process of the pegmatite, which is marked by fluid exsolution; these fluids are likely eriched in Cs and depleted in F. ③ The regular changes of chemical composition of primary muscovite and tourmaline indicate that the evolution process of vein 308 probably does not exist the addition of an external fluid. ④ The diagenesis and lithium mineralization of pegmatite No.308 are mainly controlled by fractional crystallization. The limited scale of fluid exsolution and the degree of differentiation evolution of pegmatite (only evolved to the magma—hydrothermal transition stage, not fully entered the hydrothermal stage) significant contribute to the crystallization and preservation of spodumene.