The Pl-lherzolite is located between the harzburgite and cumulates in the Hongguleleng ophiolite and parallel to the mylonitized zone at the top of the harzburgite.The Pl-lherzolite differs from the cumulates in having blastic texture and high-temperature deformed fabric of Ng[100] characteristic of the mantle peridotite and yielding orthopyroxene. In respect of mineralogy and petrology as well as strontium isotope, the Pl-lherzolite exhibits some features of transition from the cumulates to the mantle peridotite.The appearance of new-born minerals(clinopyroxene and plagioclase) in the Pl-lherzolite provides an evidence for the penetration of basic melt. The mylonitized zone may be a passage for the basic melt derived from the bottom of the magma chamber, which has penetrated into the harzburgite.From the above, the authors conclude that the Pl-lherzolite is the product of the reequilibrium between the depleted harzburgite and the basic melt.