Abstract: The magmatic activity of the Xing'an Block was strong in the Middle and Late Jurassic-Early Cretaceous.A thorough understanding of the genesis and magmatic evolution of the granite in this period, which is of great significance for improving the understanding of the Mesozoic tectonic evolution and guiding the prospecting in this area.In this paper, the Hublin pluton in the southern part of Xing'an Block is comprehensively reported from the perspectives of zircon U-Pb chronology and geochemical characteristics.The study shows that the Hoblin rock body is composed of syenite porphyry and monzonite porphyry, and the former is the main lithology.The emplacement ages are 157 ±1 Ma and 139 ±1 Ma respectively, which were formed in the Late Jurassic and Early Cretaceous, reflecting the tectono-magmatic events of the early Late Mesozoic.In terms of geochemical characteristics, the two lithologies are characterized by moderate degree of differentiation, rich alkali, rich sodium, quasi(weak) aluminum and SiO₂-P₂O₅ negative correlation, combined with the features of high Zr content(276.3×10^-6~499.5×10^-6) and high zircon saturation temperature(788~881℃), the granite is classified as I-type granite of high potassium calc-alkaline potassium basalt series, which is transitioned to A-type granite.The total rare earth content of rock mass is medium to high, and weak negative europium is abnormal.The light rare earth is enriched while heavy rare earth is deficient, the large ion lithophile elements(Rb, Ba, Th, U, K) are enriched and the high field-strength elements(Ta, Nb, P, Ti) are depleted, especially in enesite porphyry.The crustal thickening and partial melting may be the main formation mechanism of the rock mass, combined with regional tectonic evolution, which was formed in the post-collision environment after the closure of the Mongolian-Okhotz Ocean, and the regional stress field changed from compression to extension.It is further inferred that the closing time of the Mongolian-Okhotz Ocean in the southern part of the Xing'an Block was earlier than 157 ±1 Ma.