Abstract: Numerous Paleozoic ophiolitic mélange, accretionary complex and plutons are exposed in the Alxa region, located in the central segment of the Central Asian Orogenic Belt, which may record the reworking process of continental crust during the closure of the Paleo−Asian Ocean. In this study, we collected and compiled new published data of zircon U−Pb age, whole−rock major and trace element and zircon Hf isotope for ophiolitic mélange and plutons in the southern Alxa. Based on these new data, we propose that Permian SSZ−type ophiolitic mélange and Middle−Late Permian high−Mg diorites and adakites support the hypothesis that a Permian oceanic slab subduction in the southern Alxa. The zircon U−Pb ages of Carboniferous−Permian magmatism show a younging trend toward the northwest in the southern Alxa region, indicating a northward accretion of the Alxa Block. Temporal−spatial variations of zircon Hf isotope for plutons suggest tectonic switching from advancing to retreating subduction during Carboniferous–Early Triassic within the southern Alxa.