Southwestern margin of the Ordos Block in the Paleo—Mesoproterozoic is a part of the rifts of the southern margin of the North China Craton, previous studies mainly focus on the 1. 85~1. 75 Ga granites exposed in the research area, but later than 1. 85 Ga intermediate—basic eruptive rock in the Proterozoic has not been reported. Basaltic andesite at the Tiemahe section is exposed in the Liupanshan faults zone in the southwestern margin of the Ordos Block with amygdaloid structure and porphyritic texture. The phenocrysts are mainly composed of plagioclase and small amount of mafic minerals. SHRIMP zircon U- Pb dating results show that the Tiemahe basaltic andesite was erupted in the early Mesoproterozoic (ca. 1740±14 Ma). Geochemically, the rock samples show low SiO2, TiO2, K2O, and high Na2O, FeOT and Al2O3. and display LREE- enrichment patterns, with LREE/HREE ratios of 6. 50~7. 00, (La/Yb)Nof 5. 62~7. 14, and δEu of 0. 69~0. 91. In the spider diagrams, they are enriched in large ion lithophile elements (e.g., Ba, Th, U, K) and relatively depleted in Nb, Sr and Ti. The values of (87Sr/86Sr)i(0. 70587~0. 70934)，εNd(t) (-6. 9 ~ -4. 8), Nb/Ta (6. 6~8. 3) and TDM (2562~2730 Ma) suggest that the Tiemahe basaltic andesite was originated from enriched lithospheric mantle that had been metasomatized by subducted slab derived fluids, which may be related with late Paleoproterozoic orogeny in the western margin of the Ordos Block. This paper suggests that the Tiemahe volcanic rocks were generated by decompression melting under intracontinental extension, which reverify that the western Ordos Block was involved in tectonic processes of the intracontinental extension of the NCC in the Mesoproterozoic.