Abstract: In recent years, significant breakthroughs have been made in the exploration of fluorite deposits in the eastern Kunlun mountains of Qinghai Province. Main fluorite ore bodies in the newly discovered Kayakedeng deposit are mainly located near the outer contact zone of the K-feldspar granite and are controlled by the NW and NNW-trending faults. The host rocks are marble and gneiss of the Jinshuikou Group. The ores are mainly in the form of blocks, bands, vein-like and brecciated structure. The mineral composition of ore mainly consist of fluorite, calcite and quartz. However, there is still a lack of research on the mineralization age and formation mechanism of the fluorite deposit. This paper, through methods of isotopic chronology and geochemical analyses of rare earth element, focuses on studying the ore-forming age, redox conditions and the genesis of the deposit. The results show that the Sm-Nd isotopic age of fluorite is 402 Ma, and the zircon U-Pb age of K-feldspar granite is 404 Ma, indicating that they were formed simultaneously. Furthermore, based on the chondrite-normalized rare earth element distribution pattern, the abnormal characteristics of Ce and Eu elements, as well as the diagrams of (Y/Ho-La/Ho) and (Tb/Ca-Tb/La), it is demonstrated that the fluorite deposit is of hydrothermal origin and has the characteristics of a synchronous and homogenous mineralizing fluids. It is speculated that the fluorite deposit has an etiological connection with the K-feldspar granite. Based on the above research results, it can be further suggested that the main source of the Ca is from marble, and F is mainly from K-feldspar granite. The deposit was formed under the extensional tectonic background, with the ore-bearing fluids filling and substituting along the fracture-vein system.