The Aizi pluton in the north of Guangdong is located in the central-western part of the Guidong complex pluton and consists of biotite granite. Currently, research on the formation age and genesis of this rock mass is weak, which is helpful to perfect the magmatic activity pedigree in the eastern Guizhou area, and provide new constraints on the petrogenesis and tectonic background. In this paper, LA-ICP-MS zircon U-Pb chronology, mineral-petrogeochemistry and Hf-Nd isotopes have been studied for Aizi biotite granite. The mineralogical characteristics indicate that the zircons in the Aizhi biotite granite are magmatic zircons, and the apatites are fluorapatites. The zircon U-Pb dating results indicate that the emplacement age of the Aizhi biotite granite is 159±1 Ma, which is a product of the early Yanshanian in South China. The geochemical characteristics of the rocks reveal a SiO₂ content ranging from 67.93% to 69.80%, a high total alkali content (K₂O+Na₂O=7.32% to 7.53%) and A/CNK ratio of 0.95 to 0.99. The rocks are enriched in Rb, Th, and U, while depleted in elements such as Ba, Nb, Ta, Sr, Zr, and Hf. The LREE/HREE ratio varies between 7.24 and 10.17, with a pronounced negative Eu anomaly (δEu=0.43 to 0.50). The εHf(t) values of the Aizizi biotite granite range from -8.7 to -5.4, while the εNd(t) values range from -9.3 to -9.1, corresponding to t_DM2 values of 1 725～1 519 Ma and 1 711～1 689 Ma, respectively. The above geochemical and isotopic characteristics indicate that the Aizhi biotite granite belongs to the high-potassium calc-alkaline series, quasi-aluminous S-I transitional granite, which is mainly formed by partial melting of Paleo-mesoproterozoic crustal-derived arenite under medium to high temperature and low pressure. Comprehensive studies suggest that the Aizhi biotite granite formed in a tectonic setting of lithospheric extension and thinning caused by the subduction of the Pacific plate.