The Upper Cretaceous Jingzhushan Formation (K2 j ), distributed discontinuously along the Bangong Co- Nujiang suture zone with an approximately E- W trend, is a continental deposit followingthe ocean- continent fully completed conversion.Due to its large east- west spatial span, its exact formation time and the tectonic environment of the sandstones’ source area are controversial.We have collected the coarse sandstone of the Jingzhushan Formation from northern region of Geji County, Tibet, and analyzed the characteristics of detrital zircon LA- ICP- MS U- Pb age, and the main and trace elements of the sandstone. The U- Pb concordia age of sandstones from the Jingzhushan Formation is concentrated at 100~130 Ma and 150~170Ma. The zircon age shows two peaks of 111.7 Ma and 160.1 Ma on the detrital zircon age spectrum map of the Jingzhushan Formation sandstone. The latest detrital zircon weighted average age is 105.3 Ma, indicating that the Jingzhushan Formation should have been deposited after the early Cretaceous. The content of SiO2 was 52.92%~69.47%.The content of Al2O3 was 5.22%~14.34%.High field strength elements Ta, Nb and Ti are depleted, while there is enrichment of Hf, Th and REE. Large ion lithophile elements Ba are depleted, and there is enrichmentin Rb and K. The characteristics of the main and trace elements and the discriminant diagrams show that the tectonic background of the source area of sandstones from the Jingzhushan Formation in the study area should be continental island arc, and the original rock of the Jingzhushan Formation sandstones is intermediate- acid igneous rock.