In this study, we examine the pegmatite and migmatite exposed in the Qiemuerqieke area to investigate the enrichment characteristics of rare metals in the initial pegmatite- forming melt derived from the anatexis of metasedimentary rocks. We analyzed the geology, whole- rock geochemistry, and mineral chemistry of micas from the migmatite, pegmatite, and surrounding metasedimentary rock (two- mica schist). The results show similarities in mineral assemblages and chemical compositions between the pegmatite and leucosome, along with complementary trace elements between the pegmatite and melanosome. This observation supports the anatexis origin of the Qiemuerqieke pegmatite. Furthermore, the increasing content of Li, Be, Nb, Ta, Rb, and Cs in muscovites from two- mica schist to leucosome and finally to pegmatite indicates progressive enrichment of rare metals during anatexis and aggregation processes from the leucosome to the pegmatite. Notably, Be and Ta showed a significant increase, with their concentrations rising by at least three times. Additionally, low- temperature dehydration melting of muscovite and the residual phase dominated by biotite appear to restrain the enrichment of Li, Rb, and Cs in the melt, but have no effect on Be concentrations. Given the extensive Be mineralization observed in the Altay pegmatite, it is reasonable to deduce that the Altay pegmatite probably originated from the anatexis of metasedimentary rocks.