The Motuo area is located in the east of the Eastern Himalayan Syntaxis. There outcrops a sequence of high-grade metamorphic rocks, such as metapelites. Petrology and mineralogy data suggest that these rocks have experienced three stages of metamorphism. The prograde metamorphic mineral assemblages (M1) are mineral inclusions (biotite + plagioclase + quartz ± sillimanite ± Fe-Ti oxides) preserved in garnet porphyroblasts, and the peak metamorphic assemblages (M2) are represented by garnet with the lowest XSps values and the lowest XFe# ratios and the matrix minerals (plagioclase + quartz ± K-feldspar + biotite + muscovite + kyanite ± sillimanite), whereas the retrograde assemblages (M3) are composed of biotite + plagioclase + quartz symplectites rimming the garnet porphyroblasts. Thermobarometric computation shows that the metamorphic conditions are 562–714°C at 7.3–7.4 kbar for the M1 stage, 661–800°C at 9.4–11.6 kbar for the M2 stage, and 579–713°C at 5.5–6.6 kbar for the M3 stage. These rocks are deciphered to have undergone metamorphism characterized by clockwise P-T paths involving nearly isothermal decompression (ITD) segments, which is inferred to be related to the collision of the India and Eurasia plates.