Anatexis is a common phenomenon in high-grade metamorphic rocks and one of the important geological processes for tectonic evolution of orogenic belt. Eclogite is the main rock type for studying continental subduction, ultra-high pressure(UHP) metamorphism and crust-mantle interaction. Its partial melting is closely related to crustal growth, slab exhumation, and element transport and distribution in a continental subduction channel. In-situ and in source leucosomes representing the anatexis is generally retained in the Xitieshan eclogite in the North Qaidam UHP metamorphic belt, which provides favorable conditions for understanding the effect of the anatexis of the UHP eclogite. In this paper, zircon U-Pb chronology analysis was used for the leucosome in Xitieshan eclogite. LA-ICP-MS U-Pb dating yielded a weighted mean 206^Pb/238U age of 425.3±5.9Ma (MSWD=0.74), representing the formation age of leucosome.The anatexis of eclogite in the Xiteshan terrane was simulated by thermodynamic and trace element modelling, and combined with the retrograde P-T paths of eclogite in the area, the temperature and pressure conditions of equilibrium crystallization of Na-rich leucosome in eclogite were limited at 12.27~10.71kbar/794~797℃. The initial partial melting of the eclogite occurred at the eclogite phase (~19.54kbar/~780℃), and the partial melt formed in the UHP eclogite through breakdown of omphacite with minor involvement of phengite and zoisite in the process of temperature rise and pressure fall. During the whole partial melting process, the eclogite produced ~8~9vol% melt, meeting the minimum requirements of the melt migration, indicating that the eclogite may have little contributionto the source area of the syn-exhumation granite in the Xiteshan terrane.