Nominally anhydrous minerals, i.e., clinopyroxene (Cpx), orthopyroxene (Opx) and olivine (Ol), from peridotite xenoliths hosted by Cenozoic basalts in Muchang, Maguan, southeastern Yunnan Province, were investigated by micro-Fourier transform infrared spectrometry (FTIR). Most of Ol and all the Cpx and Opx grains contain structural water in the form of OH. The range of the average core water content (H₂O) of multi grains (>10) in the same sample from the analyzed Muchang peridotites is 160×10^-6~557×10^-6, 85×10^-6~207×10^-6 and 5×10^-6~12×10^-6 for Cpx, Opx and Ol respectively. The whole-rock water content recalculated according to mineral volume proportions varies from 46×10^-6 to 137×10^-6, much richer than that in the North China Craton. Elemental fractionation suggests that the peridotite xenoliths are relicts of primary mantle with partial melting. Low (La/Yb)_N (0.22~0.57) and high Ti/Eu (4 076~6 772) of clinopyroxenes suggest that Muchang lithospheric mantle has undergone low mantle metasomatism by silicate melt. Apparently, the large-scale Neo-Tethys oceanic crust subduction and fluid metasomatism contributed to the rich water in Muchang, which implies that the mantle in Muchang was the new proliferative mantle and the geological evolution differed from that of the North China Craton in Cenozoic.