Two kinds of mantle peridotites are recognized in Rutog at the westernmost part of the Bangong Lake - Nujiang ophiolite mélange in Tibet. One is a brecciform harzburgite, composed of about 80% olivine with Fo 90.76～91.84, 91.09 on average, 15% orthopyroxene with Mg# 90.97～91.41, 91.16 on average, 2% clinopyroxene with Mg# 93.24～94.60, 93.96 on average, and 3% magnetite and light brown chromium spinel with Cr# 0.20～0.25, 0.23 on average (lower than 0.60), and characterized by low MgO (41.41%～42.02%), high Al2O3 (1.63%～1.94%), CaO (1.34%～1.60 %) and Ti (133.04～134.52 μg/g), and depletion of REE with ΣREE being 0.17～0.22 times that of chondrite. Major and trace element characteristics indicate that the brecciform harzburgite is restite resulting from 10%～15% partial melting of primitive mantle. The other type is massive harzburgite without clinopyroxene, composed of about 85% olivine, 13% orthopyroxene, and 2% magnetite and red_brown chromium spinel with Cr# 0.69～0.74, 0.71 on average (higher than 0.60). In contrast to the brecciform harzburgite, the massive harzburgite is characterized by high MgO (42.96%～44.69%), low Al2O3 (0.23%～0.61%), CaO (0.08%～0.11%) and Ti (68.55～68.82 μg/g), and considerable depletion of REE, with ΣREE being 0.03～0.05 times that of chondrite. Major and trace element characteristics suggest that the massive harzburgite is restite formed by 30%～40% partial melting of the primitive mantle. It is preliminarily held that the brecciform harzburgite is restite of ancient oceanic lithosphere emplacement in the orogeny zone, and that the massive harzburgite is restite formed by another partial melting of residual peridotites during the subduction of ancient oceanic lithosphere. They are typical mantle peridotites of MOR- and SSZ-type ophiolite, respectively, and consistent with the two types of lavas in Bangong Lake ophiolite mélange, i.e., P-MORB and Boninite.