This paper provided petrographic, LA- ICPMS U- Pb dating of zircon and monazite and geochemical analysis of the early biotite granite and the late granite pegmatite in the Ganfang granite pluton from the Yifeng area, located in the eastern part of the Jiangnan Orogenic Belt.Methods: Based on the fieldwork, through the microscopic observation, the whole rock chemical analysis of the LA- ICP- MS U- Pb isotopic chronology of zircon and EPMA of monazite.Results: The zircon ages and monazite ages of biotite granite are 145. 4±1. 1 Ma and 145. 6±1. 1 Ma, respectively. The 206Pb/238 U ages of monazites and zircons from the biotite granite are consistent with the detrital zircons in the Proterozoic Shuangqiaoshan Group. The monazite 206Pb/238 U age of granite pegmatite is relatively concentrated at 139. 5 ± 0. 9 Ma. The monazites of pegmatite and biotite granite have similar EPMA data. In genetic discriminant maps of monazite, pegmatite and biotite granite have a clear linear relationship and are distributed in the range of magmatic origin. The zircons of the biotite granite exhibit an △FMQ ranging from -5. 36 to -0. 77 (with an average of -2. 84) and a saturation temperature (Ti) ranging from 668 to 757℃ (with an average of 710℃). These characteristics, marked by low oxy fugacity and low temperature, indicate the potential for forming tin, tungsten and other oxidization- type metal ore. 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 zircon from the crustal- derived granites. The zircon trace element diagram shows that the biotite granite has the characteristics of continental crust, an S- type and a highly evolved granite. Conclusions: The Ganfang granite pegmatite should come from the late evolutionary differentiation of the biotite granite, likely through the partial melting of metamorphic sandstone and mudstone in the Shuangqiaoshan Group.