The correlation between deformation and metamorphism, the evolution of metamorphic minerals and thermometry in the khondalites in the north part of Helan Mountains are consistent with a clockwise PTt path for the rock. The prograde sector is documented by the syn- to post-D_1~2 mineral assemblages, i.e. biotite ± muscovite + plagioclase + quartz in the intercalated beds of residual muscovite-biotite schists and kyanite + garnet, the kyanites are preserved in garnets or sillimanite aggregate as relic. Near-peak temperature, 750-800 ℃ at 0.6GPa, was reached syn- to post-D,, its characteristic mineral assemblages are sillimanite + garnet + cordierite + biotite + K-feldspar + plagioclase + quartz in Al-rich gneisses and orthopyroxene ± biotite + garnet + plagioclase + quartz and orthopyoxene + clinopyroxene + biotite + hornblende + plagioclase + quartz in hypersthene granulites. Post-peak stage is related to crustal lift and D_3 strong deformation belts and resulted in the formation of new cordierite at the expense of garnet + sillimanite + quaratz assemblage during the process of near-isothermal decompression (ITD). Subsequent low P, near-isobaric cooling led to the formation of andaluzite and cordierite assemblage. The PT evolutional pattern is similar to that of collision orogens of continental crustal. As the peak pressure is only about 0.6GPa and the amplitude of ITD is only 0.2GPa, it indicates that the khondalites lied in about 20km depth of the crust depth profile, and also shows the small amplitude of crustal tectonic thickening and subsequent crustal thinning and returning caused by gravitational equilibrium. The correlation between deformation and metamorphism, the evolution of metamorphic minerals and thermometry in the khondalites in the north part of Helan Mountains are consistent with a clockwise PTt path for the rock. The prograde sector is documented by the syn- to post-D_1 ~ 2 mineral assemblages, ie biotite ± muscovite + plagioclase + quartz in the intercalated beds of residual muscovite-biotite schists and kyanite + garnet, the kyanites are preserved in garnets or sillimanite aggregate as relic. Near-peak temperature, 750-800 ° C at 0.6 GPa , was reached syn- to post-D, its characteristic mineral assemblages are sillimanite + garnet + cordierite + biotite + K-feldspar + plagioclase + quartz in Al-rich gneisses and orthopyroxene ± biotite + garnet + plagioclase + quartz and orthopyoxene + clinopyroxene + biotite + hornblende + plagioclase + quartz in hypersthene granulites. Post-peak stage is related to crustal lift and D_3 strong deformation belts and resulted in the formation of new cordierite at the expense of garnet + sillimanite + quaratz assemblage during the process of near-isothermal decompression (ITD). Subsequent low P, near-isobaric cooling led to the formation of andaluzite and cordierite assemblage. The PT evolutional pattern is similar to that of collision orogens of continental crustal. As the peak pressure is only about 0.6 GPa and the amplitude of ITD is only 0.2 GPa, it indicates that the khondalites lied in about 20 km depth of the crust depth profile, and also shows the small amplitude of crustal tectonic thickening and subsequent crustal thinning and returning caused by gravitational equilibrium.