The Xiaomiao Formation is a set of the Mesoproterozoic amphibolite facies metamorphic strata，which is an important part of Precambrian basement rocks exposed in the Eastern Kunlun orogenic belt．The detailed wild-field geological mapping and indoor study shows that the Xiaomiao Formation is mainly composed of felsic metamorphite combination with basic metamorphite，which can be divided into four rock members：quartzite unit，Al-rich gneiss unit，felsic gneiss unit and quartzite-arkose quartzite unit．The petrology，geochemistry and discrimination diagrams indicate that the protolith of quartz schist and gneiss with Al-rich minerals is pelitic rock，the protolith of quartzite and arkose quartzite is sandstone or greywacke or silicalite，the protolith of amphibolite is tholeiite．It also shows that the provenance of metasediment is characterized by mid-low weathering degree which lie in cold or drought region（maybe tectonically active region），is mainly composed of felsic rock with less alkali feldspar and mixed with basic volcanic rock in the protolith．Taking all factors into consideration，the metasediment from the Xiaomiao Formation formed in intracontinental extensional taphrogenic trough or rift basin，the metabasite formed in a continental rift environment during initial or late，which indicates that the Xiaomiao Formation formed in intracontinental rift environment．