Abstract: The Yifeng area in the eastern part of Jiangnan Orogenic belt is an important metallogenic area for Nb, Ta, Be, Li and other rare metals in China. The ore deposits are closely related to the Mesozoic Ganfang granite body. Although the predecessors have done a lot of work on the age of Ganfang granite body, there are few studies on its genesis. In recent years, with the discovery of Be-rich granite pegmatite, the complexity of diagenesis and mineralization has been added. In this paper, LA-ICPMS U-Pb dating and geochemical analysis of biotite granite and granite pegmatite in Ganfang granite body have been carried out. The results show that the Th/U values of biotite granite zircons range from 0.11 to 0.78, and the weighted average age is 145.40±1.17 Ma. The Th/U ratio of monazite is from 6.5 to 178.4, and the weighted average age is 145.61±1.13 Ma. The 206Pb/238U age of monazite and zircon from biotite granite are consistent with the detrital zircons in the Proterozoic Shuangqiaoshan Group. The Th/U ratio of monazite of granite pegmatite ranges from 1.2 to 50.6, and the age of 206Pb/238U is relatively concentrated, with a weighted mean age of 139.51 ± 0.87 Ma. The monasites of pegmatite and biotite granite have similar EPMA data. In the different origin discriminant maps of monasite, pegmatite and biotite granite have obvious linear relationship and are distributed in the range of magmatic origin. All kinds of granites in Ganfang granite body have certain continuity in age, and the spatial interpenetration relationship can be seen successively. Its age characteristics are as follows: biotite granite → two-mica granite → Muscovite granite → lipolite Muscovite granite → beryllium-rich granite pegmatite. △FMQ of zircons of biotite granite ranges from -5.36 to -0.77, and saturation temperature (Ti) ranges from 668 to 757℃. It has the ability to form tin, tungsten and other oxidization-type metal ore with low oxygen fugacity, low temperature characteristics magma. The standardized REE partition curve of zircon chondrites shows a left-leaning partition pattern, which is consistent with the rare earth element content and partition pattern of the shell source zircon of granite. The zircon trace element diagram shows that the biotite granite has the characteristics of continental crust, S type and highly evolved granite. To sum up, the Ganfang granite pegmatite should come from the late evolutionary differentiation of biotite granite, from the partial melting of metamorphic sandstone and mudstone in Shuangqiaoshan Group.