The closure time of the Paleo—Asian Ocean (PAO) on the northern margin of North China Plate is still unclear. The Liangtou monzogranite in Zhangbei area of northern Hebei Province is located in the central part of the northern margin of the North China Craton(NNCC), and has important implications for the PAO closure. This study carried out zircon LA- ICP- MS U- Pb geochronology and geochemistry on the monzogranite to discuss its origin, in order to provide new evidence for the closure time of the PAO. Methods: Based on petrology, geochemistry, LA- ICP- MS zircon U- Pb geochronology and Hf isotopic composition, this paper discusses the petrogenesis and tectonic setting of the Liangtou pluton, and the closure time of the PAO. Results: The zircon U- Pb LA- ICP- MS dating shows that the age of the monzogranite is 262. 5±2. 6 Ma, indicating that the pluton was emplaced in the Late Permian. The rock has higher SiO2 (70. 27%~73. 89%), Na2O (4. 2%~4. 55%), K2O (3. 87%~4. 64%), Sr (417×10-6~827×10-6), and lower Yb (0. 286×10-6~0. 518×10-6), Y (2. 74×10-6~6. 98×10-6) contents. The zircon εHf (t) values range from -17. 50 to -11. 12, with two- stage model ages (tDM2) of 1989~2390 Ma. Conclusions: The Liangtou pluton belongs to adakitic rock and arc magmatite formed in the active continental margin arc setting. It indicates that the PAO may still be in the process of subduction towards the NNCC during the Late Permian(262. 5±2. 6 Ma), and its final closure time may have been at the end of the Late Permian.