Ultra-high pressure metamorphic minerals were found in three types of eclogite in western Tianshan Mountains, inclusions of coesite pseudomorphs in garnets were detected in type I eclogites interlayered with mafic blueschists and carbonate eclogites, quartz exsolution lamellae in omphacites were recognized in typeⅡeclogites with pillow structure,and magnesite of metamorphic origin was discovered in typeⅢlenticular calcite/dolomite eclogites within Based on the study of mineralogy and petrology, the metamorphic evolution of typeⅠeclogites can be divided into three stages, i.e. pre-peak ultra-high pressure (UHP) metamor- phicstage (356~433℃, 0.8~1.0 GPa), peak UHP eclogite-facies stage (496~598℃, 2.572~2.666 GPa) and retrograde epidote blueschist_facies stage (500~530℃, 1.0~1.2 GPa). The authors have set up phase equilibrium in NCMASCH system (Na2O-CaO-MgO -Al2O3-SiO2-CO2-H2O), and the calculation shows that the peak metamorphism of mag- nesite_bearing glaucophane eclogites in western Tianshan Mountains occurred at 2.7~2.8 GPa and 525~607℃, XCO2<0.006. Consequently, the eclogites from western Tianshan Mountains have obviously undergone UHP metamorphism, and southern Tianshan orogenic belt might be the largest UHP metamorphic belt formed by subduction of oceanic crust in the world.