Objectives：The geological tectonic properties of the central and northern Gangdese belts have different understandings so far. Therefore, magmatic rock petrology, zircon U- Pb geochronology and geochemical research in the belt are of great significance. The purpose of this paper is to investigate the genesis and geodetic background of the Bengco Lake plaque- like syenogranite in order to provide basic data for the Early Cretaceous magma—tectonic evolution in the northern Gangdese, and to provide new evidence and important restraints for studying the Mesozoic tectonic evolution of the entire Gangdese. Methods：The processing of major elements, rare earths and trace elements was completed by the Huayang Mine Testing Center. The test was completed by the Chengdu Mineral Resources Supervision and Testing Center of the Ministry of Land and Resources. The main elements, trace elements and rare earth elements were detected by ICP- MS, ICP- AES, gravimetric method, etc. The analytical precision is better than 5% .Zircon single mineral separation was completed by Sichuan Huayang Rock Mine Testing Center. The Central South Mineral Resources Supervision and Inspection Center of the Ministry of Land and Resources embarked on cathodoluminescence (CL) image acquisition and LA- ICP- MS zircon U- Pb dating. Before the analysis, the instrument was optimized by the synthetic silicate glass standard reference material NIST610 which developed by the American National Institute of Standards and Technology. In order to control the stability of the instrument and control the test accuracy, one Sample 91500 and standard NIST 610 test were performed after testing 6 unknown samples using standard zircon 91500 to calibrate Pb/U isotope fractionation. The data processing uses the GLITTER (ver4.0, Macquarie University) and ISOPLOT (ver 3.0) software programs. Results: The Bengcuo plaque- like syenogranite is located in the eastern section of the northern Gangdese, and the latest stratum of the rock mass emplacement is the Middle—Late Jurassic Lagongtang Formation. The LA- ICP- MS zircon 206Pb/238U age of the plaque- like syenogranite is 116.7±1.2Ma, and the age is the early Cretaceous. The rock has high SiO2, rich Al2O3 and K2O, and is lack of TiO2, MgO and CaO. A/CNK equals 0.94~1.91 (average 1.16), belonging to the high potassium- calcium- alkaline potassium series of aluminous rocks. (La/Yb)N is 1.22~9.62, δEu is 0.04~0.38, and the rare earth element distribution pattern of chondrite is U- loss type with light enrichment of light rare earth. Large ion lithophile elements and high field strength elements Rb, K, Th, Ta, Ce are relatively enriched and Nb is relatively depleted and Ba, Sr, P, Ti are strongly depleted, showing the characteristics of colliding granite, diagene magma originating from the earth's crust . Conclusions： Based on the latest data and the research results of this paper, it is preliminarily believed that the Bengcuo plaque- like syenogranite in the fault- disrupted area may be formed in the land—land collisional tectonic setting of the Gangdese belt and the Qiangtang block, which is the partial melting of the thickening lower crust during the collision. The results also indicate that the end of the Bangong Lake—Nujiang New Tethys subduction should be earlier than 116Ma. Combined with the aging results of the region,when the Bangong Lake—Nujiang New Tethys subduction ended, the time of the Gangdese belt and the Qiangtang block land—land collision was around 120 Ma.