Abstract: Water in the upper mantle plays a critical role in the strength and partial melting of lithosphere. Investigation on water contents of peridotite xenoliths from the North China Craton (NCC) gives important constraints on mechanism for its lithospheric thinning since the Mesozoic. Spinel peridotite xenoliths were collected from Cenozoic basalt in Yangyuan, Hebei province, to study the water contents of the lithospheric mantle in the northern Trans-North China Orogen of NCC. Using microscopic Fourier transform infrared spectrometry (FTIR), we measured the water contents of major minerals in five samples. All olivine, orthopyroxene and clinopyroxene grains exhibit characteristic hydroxyl absorption peaks in FTIR spectra. Olivine has relatively low amount of water (4×10-6~9×10-6), while orthopyroxene and clinopyroxene have (105~201)×10-6 and (260~440)×10-6, respectively. Based on the modal composition, the water contents of bulk samples are estimated to be (49~75)×10-6. It is worthy to note that metasomatism and late alteration significantly increase the water contents of clinopyroxene in our amphibole-bearing harzburgite sample. Water contents in clinopyroxene and orthopyroxene from Yangyuan peridotite xenoliths display positivecorrelation with the water partition coefficient D cpx/opx OH =2.4±0.9, which is consistent with the average value (D cpx/opxOH =2.2±0.1) for the global peridotite xenoliths. Olivine, orthopyroxene and clinopyroxene in Yangyuan peridotite xenoliths contain much more hydroxyl than those from Hannuoba, which may be caused by fluid-rich metasomatism in the upper mantle beneath Yangyuan.Statistical analysis of available water measurements on natural peridotites shows that olivine from basalt-borne spinel peridotites is relatively dry with water contents of 0~10×10-6. In contrast, variable water contents in orthopyroxene and clinopyroxene from basalt-borne spinel peridotites reflect heterogeneous water distribution in the upper mantle. Olivine, orthopyroxene and clinopyroxene from kimberlite-borne garnet peridotites contain much more water than those from basalt-borne spinel peridotites.This is probably because kimberlite is characterized by greater depth of origin, more fluids and faster ascending rate than basalt.