Abstract: The tectonic setting of the Langshan area, which is located on the northeastern margin of the Alxa block in Inner Mongolia, has always been controversial. This paper presents the results of zircon U-Pb geochronology and geochemical data of pillow basalts in the Langshan area. The basalt LA-ICP-MS zircon U-Pb dating results show that most zircons from basalts were captured from basement. Based on the features of zircon and the age of granite invading basalt, the age of basalt is estimated to be ca. 254~252Ma, which falls into the Late Permian. Pillow basalt shows the characteristics of island arc basalt with its low alkali and low potassium, depletion of Nb, Ta, Ti, P, enrichment of Rb, Ba, U, enrichment of LREE, and depletion of HREE with weak Eu negative anomaly. It is preliminarily believed that basalt was formed on the active continental margin and was produced by southward subduction of the ancient Asian Ocean. The results indicate that the northern margin of the Alxa block was a continental marginal arc in the Late Permian, thus providing evidence for the study of the Late Paleozoic tectonic setting on the northeastern margin of the Alxa block.