This paper provided petrographic and geochemical characteristics, LA- ICP- MS zircon U- Pb age of the Keqikezisu granite in the western part of the East Kunlun Orogenic Belt and discussed the formation age, genesis and geological significance of the rocks. The results show that the weighted age of zircon U- Pb in the Keqikezisu granite is 442.3±4.4 Ma (MSWD=2.7), demonstrated the rocks crystallizing time is Late Ordovician to Early Silurian, which is a newly disunited Early Paleozoic granite in the region. The content of SiO2 in the granite is 68.96%~70.40%, Na2O is 3.08%~3.14%, K2O is 3.93%~4.32% , and the Al saturation index( A/CNK) ranges from 1.06 to 1.13. The granite belongs to high potassium calc- alkaline peraluminous rocks. The Keqikezisu granite is enrichment in large ion lithophile elements(LILE) K, Rb, and U, Th, radioactive elements and different degree of loss Ba, Nb, Sr, Ti, Zr, high field strength elements(HFSE). Combined with the regional data and previous results, this paper believes that Keqikezisu granite is related to subduction and collision tectonic environment, and may represent subduction of the Proto- Tethys Ocean in the western section of the East Kunlun Orogenic Belt during the Late Ordovician to Early Silurian. The results provided evidence for the tectonic evolution of the Proto- Tethys Ocean in the East Kunlun Orogenic Belt and the Early Paleozoic magmatic activity in the South Kunlun junction belt.