A variety of mantle xenoliths were entrapped in alkalic basaltsin Huangyishan,Kiandian area,Liaoning Province, resulting from volcanic e ruption during the middle Pleistocene. These mantle xenoliths are helpful to und erstand the composition and thermal structure of the upper mantle lithosphere beneat h the Kuandian area. the equilibrium temperature-pressure, bulk density and se ismic velocity of mantle xenoliths are estimated in this paper. The results show t hat the depth of Moho is ca. 35 km to 38 km, spinel lherzolites prevail in the r ange from 38 km to 65 km, transition zone from spinel pyroxenites to garnet pyroxe nites lies between 54 km and 64 km, and garnet websterites distribute in a depthfrom 54 km to 75 km. It is supposed that the lowvelocity layer in the upper man tle is below 75 km.the thermal state of the upper mantle within depths of 45 km to 8 0 km beneath Kuandian area may be formulated as: t(℃)=847.17+1.557d+0.02235d2.