Abstract: Through analyzing the geological setting，petrology，geochemistry characteristics and tectonic setting of ophiolite in Nawucuo，it is discovered that the ultrabasic rock are characterized by high Cr，Ni，Co，ΣREE，and low Mg＇value.Its major element and REE indicated that the ultrabasic rock has the comagmatic feature with altered basalt.The major elements of altered basalt indicated the characteristics of transition to alkali basalt from tholeiite.The trace elements analysis show that the distribution pattern of trace elements of altered basalt is nearly flat and the altered basalt are relative enrichment of LILE and HFSE，such as Rb，Ba，Sr，Th，Ta，Hf，but Nb is loss，which is significantly unlike the typical mid-ocean ridge basalt.The REE distribution pattern are light REE enrichment in right gently-dip type，with no obvious Eu anomaly，but negative Ce anomaly，which is similar to the characteristics of the oceanic island basalts.According to the geological characteristics of ophiolite and adopting the tectonic environment discrimination diagrams，it is determined that the geotectonic setting of ophiolite of Nawucuo is formed in spreading ocean basin.Besides that，the ophiolite is similar to the edge of the sea ophiolite，but not a typical oceanic ophiolite.

Key words: Ophiolite, Geochemical characteristics, Tectonic setting, Bangongcuo-Nujiang suture zone