The Beishan area is an important part of the Central Asian Orogenic Belt. The Tanshanzidong basic complex located west of the Beishan Dashantou complex is an important carrier to reveal the late Paleozoic tectonic evolution on the southern margin of the Central Asian Orogenic Belt. This paper reports that the Tanshanzidong basic complex was emplaced with the zircon U-Pb age of 366.0±2.8 Ma. The rocks are characterized by SiO₂ (47.83%~52.25%), K₂O (0.12%~0.45%), Na₂O (2.47%~3.19%), MgO (5.30%~9.22%) and the evolution from tholeiitic series to calc-alkaline series. The rocks are enriched in LREE with positive Eu anomalies, depleted in Nb, Ta, Zr, Ti and enriched in Rb, Ba, Sr, U, K, with the data Nb/La=0.23~0.46, Hf/Th=0.88~3.81, (⁸⁷Sr/⁸⁶Sr)_i (0.704 8~0.704 9) and εNd(t) (+3.72~+4.30), suggesting that they were formed in the arc environment of active continental margin. Based on regional geology, the authors hold that the Tanshanzidong basic complex was the product of partial melting of depleted lithospheric mantle, which was replaced by the subduction fluid during the subduction of the northward subduction of back-arc basin represented by Huitongshan-Zhangfangshan ophiolite. These results provide a direct indication for the vertical growth of the crust caused by the late Devonian crust in the Central Asian Orogenic Belt.