Abstract: The basaltic lavas from Renbu ophiolite from Xizang(Tibet)are composed of finegrained plagioclase basaltic porphyrite，coarse-grained plagioclase basaltic porphyrite，and amygdaloidal pyroxene basalt．The analytical data show that their contents of potassium and natrium are relatively higher，and those of iron and phosphorus are also higher，but calcium and magnesium are comparatively deficient． Meanwhile，they have higher aluminum and lower titanium contents and belong to tholeiite rock series．LILE，such as Ba，Rb，Sr and HFSE，including Th，Ta，Nb，Zr and Hf are rich，but Cr，Ni and the other trace elements are relatively poor, total abundances of gale earth elements are comparatively high and they display the enriched distribution patterns of LREE，which shows that the basalts possess the characteristics of the typical oceanic island-arc．The Th/Ta ratios are between 1.03 and 1.53 an d the average value is 1.19．The La/Ta ratios are between 10.08 an d 13.26 and the average value is 12.2．The Th/Ta，La/Ta ratios an d the distribution pattern s of spidergrarms indicate that the Renbu lavas are oceanic non—SSZ basalts． Intergrating with the field geology and comparing with MORB．OIB and the other typical ophiolites ，we can draw a conclusion that Renbu ophiolite was probably formed in an initial marginal basin tectonic environment under the extension stress dynamics during the Neo-Tethys periods．