Central Inner Mongolia is located in the southeastern segment of the Central Asian Orogenic Belt (CAOB). The closing time and location of the Late Paleozoic Paleo- Asian Ocean has always been controversial. Geological field investigations discovered Late Paleozoic pillow basalt developed in the Bairin Youqi, Inner Mongolia, which provided an important clue for the study of regional tectonic evolution of the Paleo- Asian Ocean. Geochronology, petrography and geochemistry show that the LA- ICP- MS zircon U- Pb concordia age of the pillow basalt is 256. 6±2. 6 Ma and it was formed in the Late Permian. The pillow basalts are characterized by low SiO2 (average 48.73%), low TiO2(average 1. 47%) and high Al2O3 (average 17. 17%), which show the transition type between subalkaline basalt and andesite/basalt, and the Mg# values are lower than the original magma value of mantle- derived magma (68～72). The normalized REE distribution curve of chondrite is weak to right- leaning and is nearly flat, which is similar to the REE distribution characteristics of the typical E- MORB. Pillow basalts are relatively enriched in large iron lithophile elements (LILEs: Rb, Ba, Th and U), with a slight enrichment of high field strength elements (HFSEs: Nb and Hf), and have geochemical characteristics of the E- MORB. Compared with the previous studies, combined with the characteristics of the major element geochemistry, trace element geochemistry, tectonic environment and isotope geochronology of the pillow basalts, it is considered that the pillow basalts in Bairin Youqi, Inner Mongolia are similar to the composition of the ophiolite in the supra subduction zone (SSZ), which were formed by the mixing of depleted mantle and enriched mantle during subduction of the Paleo- Asian Ocean plate, indicating that there was still a remnant ocean basin of the Paleo- Asian Ocean in the region in the Late Permian. Our comprehensive analysis shows that the Paleo- Asian Ocean finally closed in the Late Permian- Early Triassic.