///The mafic-ultramafic rocks from northern Guangxi have been dominantly classified as calc-alkaline and tholeiite series. The content of SiO2 and MgO change a wider range. The mafic-ultramafic rocks show steep right-dipping and the depletion of Sr and Hf in primitively mantle normalized patterns. The REE distribution patterns of the rocks also show steep right-dipping and positive Yb anomaly. These show features of island arc volcanic. The rock tectonic environment is analysed. The results show that it is not a single factor. The petrogenesis may be caused by a small median ridge closed and it may be the products of plates convergence rather than derived from mantle plume.