We investigate 3-D thermal and rheological structures of the lithosphere beneath Northeast China using detailed P- and S-wave velocity models following mineral physics as well as geothermal methods. Small-scale temperature changes and thermal lithosphere thickness variations between different tectonic blocks are revealed. Our results show that strong lateral heterogeneities exist in the lithospheric thermal structure and rheological structure on both sides of the North-South Gravity Lineament (NSGL). The Changbai volcanic area and the central part of the Songliao Basin in the eastern side of the NSGL exhibit higher temperatures, thinner thermal lithosphere and lower rheological strength, which are closely associated with the western Pacific plate subduction under the Eurasian continent, resulting in upwelling of wet and hot asthenospheric material above the stagnant Pacific slab in the mantle transition zone. The thermo-chemical erosion of the upwelling asthenospheric material may induce delamination of partial lithosphere under the Songliao Basin. In addition, the western and southern edges of the Songliao Basin are characterized by lower temperature, thicker thermal lithosphere and higher rheological strength, which may indicate a relatively stable lithosphere. The Halaha and Abaga volcanic areas in the western side of the NSGL exhibit higher temperature, thinner thermal lithosphere and lower rheological strength, which could be caused by small-scale upwelling of hot asthenospheric material associated with delamination of partial lithosphere beneath the Songliao Basin.