Abstract：The Jibusi Ta-Nb rare metal deposit, accompanied by Li-Rb-Cs mineralization, is a medium-sized Ta-deposit located in the southwest of the Daxinganling rare metal metalization belt. In this paper, through systematic petrographic analysis, rock geochemical analysis and LA-ICP-MS U-Pb chronology analysis of tantalum-niobium, the diagenesis and metallogenic mechanism of the deposit and ore-forming rock were studied. The lithology of ore-forming granite in Jiabusi deposit is mainly jadeite-lithium muscovite-alkalic feldspar granite and lithium muscovite-albite granite. The geochemical data of ore-forming rock shows that their major elements are rich in silicom,aluminum and alkali, but poor in iron, magnesium and calcium, very poor in titanium and phosphorus, which belongs to the peraluminous high potassium calcium alkaline series. Their trace elements are rich in Rb, Th, Nd and Zr, poor in Ba, Nb, Sr and P, strong depleted in Ti. Their rare earth elements (REEs) show very lower ∑REE with average value is 47.97×10-6, have strong negative Eu anomaly and significant M-type “tetradeffect ”. The Zr/Hf of ore-forming granites are between 2.58~3.47，Nb/Ta are between 0.3~0.39, which indicate its belong to Ultra (or extremely) fractionated granite. The ore minerals in Jiabusi deposit are microlite, manganotantalite and Li-muscovite, with Rb and Cs are mainly present in minerals such as lithium mica and tantalum niobium in a similar texture. This paper reports the U-Pb dating results of different granites in the deposit by using LA-ICP-MS method. Zircon U-Pb age of ore-free biotite (hornblende) granite was 144.0±1.0 Ma (2σ, n=16, MSWD=1.3), which represents the diagenetic age of the surrounding rock Narenwula intrusive body. The weighted average age of 206Pb/238U of magmatic tantalum-niobium minerals in mineralized alkalic feldspar granite was obtained at 120.7 ± 0.2 Ma (2σ, n=17/18, MSWD=6). It shows the mineralization age and the diagenetic age of the Jiabusi ore-forming granite intrusion are late phase of Early Cretaceous, which are related to the lithospheric extension after the closure of the Mongolian-Okhotsk Ocean in the Middle Jurassic. The author indicated that the formation of Jabusi deposit can be divided into two stages. The first stage is the primary crystallization stage of magma, which is dominated by Ta and Nb mineralization. The second stage is the self metasomatism stage of hydrothermal fluids, which is dominated by li, Rb and Cs mineralization. Around the Narenwula intrusive rock foundation, there still has the potential of finding rare metal deposits as the same type.