The Koktokay No. 3 pegmatite dyke is famous for its overall shape of a hat, concentric zonation pattern, and complex rare- elemental mineralization assemblages. The magma of the Koktokay No. 3 pegmatite is heterogeneous and highly evolved. The main emplacement mechanism for the No. 3 pegmatite dyke involves upward intrusion of the pegmatite magma along gently inclined joints and stay in place in the form of a solid hat with the help of periperal faults. After emplacement, the pegmatite magma experienced three stages of melt, melt- fluid and late hydrothermal accompanied by mineralization of Be- Nb- Ta, Li- Be- Nb- Ta and Ta- Cs- Rb- Hf, respectively. Fractional crystallization and liquid immiscibility control the enrichment and deposition sequence of rare elements in the Koktokay No. 3 pegmatite and hydrothermal replacement may have played a role on redistribution of the rare elements. The strong fractional crystallization of the outer zones (Ⅰ～Ⅳ) and large fluid exsolution between zones Ⅳ and Ⅴ are favorable for the magma to achieve lithium saturation concentration and the system to begin lithium deposition. An important future research focus should be on the detailed description of melt- fluid evolution process, further analysis of metallogenetic mechanism of the rare elements, a thorough discussion on the genesis of magma, influence of P, F, B, Li and CO2 on rare metal mineralization, and deep prospecting along the gently inclined brim.