Field geological survey shows that there are many eclogite lenses outcropped in the Altun Mountains Rock Group which extends for 300 km from the Qiemo River in the west to Mangya in Altun area. Eclogite can be divided into two types according to its modes of occurrence and petrologic characteristics. One is characterized by medium-fine grained texture, massive structure, no gneissosity, weak retrogressive metamorphism, and a close relation to gneissic granite or granodiorite; mineral assembly of the early period is garnet + omphacite + quartz, and that of the late period is amphibole (or pyroxene) + plagioclase + quartz; omphacite has remarkably different Al2O3 and FeO content, while its CaO, MgO and Na2O content is relatively stable: Al2O3 is generally 5.55%～9.50%, FeO 4.33%～7.53%, and NaO 3.05%～5.54％; jadeite content is 15.39～27.49％ with an average of 22.22%; the end member compositions of pyroxene are between those of kyanite eclogite and gneiss eclogite; Chemical composition of garnet varies a lot with ∑FeO 18.82%～30.58%, MgO 2.38%～13.67%, and CaO 4.65%～10.26%, while SiO2 and Al2O3 change insignificantly, being 35.63%～39.57% and 20.92%～23.65% respectively; the average end member composition of eclogite (mostly being Mg- and Ca-rich almandine) is assigned to C type eclogite in Coleman's classification diagram (1965). The other is characterized by fine-grained texture, gneissic structure, penetrative geissosity, and obvious retrogressive metamorphism, with its wall rocks mostly related to marble, biotite granulite, quartz schist etc; a majority of this type of eclogite has been changed into garnet amphibolites with obvious retrogressive metamorphism; the eclogite is confined to Palaeoproterozoic Altun Mountains Rock Group and is comparable to the eclogite on the nortern margin of Qaidam Basin in the aspect of either wall rock characteristics or eclogite property, suggesting similar geneses; moreover, granitic gneisses as the wall rocks of eclogite have basically the same diagenetic age［（930±42）～（686±20） Ma］ and metamorphic ages［（525±31）～（434±29） Ma］as the eclogite. These similarities show that these two types of eclogite were both formed in Early Paleozoic by deep subduction of Late Proterozoic crust materials. The eclogite-bearing Altun structural complex belt is the westward extending part of the northern Qaidam Basin collision complex belt.