The Yueyashan-Xichangjing ophiolite, which locates in the mid-belt of Bei Shan, is the most complete ophiolitic mèlang in Bei Shan. The Chondrite-normalized REE patterns of the mafic rocks of Yueyashan-Xichangjing ophiolite are of characteristics of LREE depletion, similar to N-MORB, while the spider diagram shows the enrichment of the large iron lithosphile elements (LILEs), and depletion of high field strength elements (HFSEs)-the unique feature of the arc volcanic rocks, namely they have the MORB-like and arc-like geochemical features, similar to the Kuerti ophiolite which formed in back-arc basin. The εNd of samples are positive and high（6.11~8.17），which implies that the source area is the depleted mantle. According to the geochemical and sedimentary characteristics, the tectonic setting of the Yueyashan-Xichangjing ophiolite would be a back-arc basin. The Yueyashan-Xichangjing ophiolite ought to form in the oceanic basin which constitutes the “arc-basin” system in the north of Tarim plate, with the Xieshan-Dongqiyishan volcanic arc in the north.