Liemai muscovitegranite, located in the eastern segment of the Tethyan Himalaya belt, intruded into the lowgrade metamorphic rocks of the marginal of Yardoi dome in early Paleozoic era. Zircon UPb dating, Hf isotopic composition and wholerock geochemistry of the Liemai muscovitegranite rocks have been carried out to constrain its formation age and petrogenesis. The results show that the Liemai muscovitegranite rocks have high SiO2 (71.08%～71.49%), Al2O3(15.55%～15.72%), K2O(4.32%～4.57%), A/CNK ratios (1.17～1.21) and low CaO/Na2O ratios (0.22～0.28), suggesting that the rocks belong to highK calcalkaline peraluminous leucogranites. The REE diagram shows enrichment of Rb, Th, K, La, Nd, Hf and Y, and depletion of Ba, Nb, Sr and Ti. These rocks are highly enriched in LREE (LaN/YbN=59.96～79.85) and depleted in HREE (LaN/GdN=6.28～6.51), with LREE/HREE=16.57～17.91 and slightly negative Eu anomalies (δEu=0.78～0.79). In contrast to twomica granite from the margin of Yardoi Dome, the Liemai muscovite granites have relatively high Rb contents (204.1×10-6～293.8×10-6) and Rb/Sr ratios (1.52～2.20), relatively low Sr contents (<134.6×10-6) and Sr/Y ratios(23.94～27.73), and more obvious HREE fractionation. Zircon LAICPMS dating yields the youngest rim age of 485±11Ma (MSWD=21), representing the crystallization age of the Liemai muscovitegranite, which should be earliest age reported to date. The εHf(t) values of the zircons vary from -6.4 to -2.3, implying a crustal origin. The twostage Hf model age varies in the range of 731～839Ma, indicating that source rocks are Neoproterozoic in age. The ages of inherited core zircons vary between 135.7Ma and 3339.2Ma, indicating that the source rocks of the Liemai Leucogranites may be EarlyCretaceous sedimentary rock. It can be proposed that, during the main collision stage between the Indian and the Eurasian plates, crustal thickening in company with increasing pressure and temperature resulted in partial melting of the EarlyCretaceous sedimentary rocks, giving a rise to the formation of the Liemai muscovitegranite.