Exposed in the Ailaoshan ophiolito belt and typically representing Paleotethyan ophiolites, the Shuanggou ophiolites are composed of metaperidotite,gabbro, diabase and basalt. Chemically, metaperidotite is of LREE-enriched type, resulting Probably from the metasomatism of components enriched in large-ion lithophile elements (LILE). The melt formed by partial melting of the mantleis depleted in LREE, whereas in diabase and basalt, there exist both LREE-depleted type and LREE-enriched type, with the former corresponding to N-MORB and the latter to E-MORB. It is considered that the LREE-depleted type was derived from the depleted mantle source, while the LREE-enriched type experienced an event of LREE and LILE enrichment. The REE characteristics of Shuanggou ophiolites imply that they might have been formed in a back-arc basin environment.