The distribution of Permian- Triassic magmatic rocks in western Yunnan Province is still unclear, resulting in controversy regarding the Paleo- Tethyan tectonic evolution model. Here, we present new LA- ICP- MS zircon U- Pb, zircon Hf isotopes whole- rock major and trace element, and Sr- Nd isotopic data for the Shuixie grabbos of the western Langping- Simao basin in the Sanjiang Orogen, SW China. The zircon U- Pb ages of two samples from Shuixie gabbros are 237.8±3.4 Ma and 240.8±3.3 Ma respectively, representing their crystallization age and belonging to the Middle Triassic. The samples have high Na2O/K2O (3.81~49.14), and are enriched in LILEs ( such as Ba, Rb, Th, U), depleted in HFSEs (such as Nb, Ta). The REEs are weakly fractionated, and the LREEs are weakly enriched. The δEu values ranges from 0.87 to 1.07, without obvious Eu anomaly. Zircon εHf(t) values are all positive, mainly ranging from +5.67 to +15.75. The initial 87Sr/86Sr ratio of the whole rock ranges from 0.70453~0.70776, and εNd(t) values are all positive, ranging from +4.9 to +5.2. Geochemical characteristics show that Shuixie gabbros originated from the partial melting of the depleted mantle, and the fractional crystallization of mafic minerals and Fe- Ti minerals occurred during the magmatic evolution. Shuixie gabbros are located at the junction of the Jiangda- Weixi arc and the Yunxian arc, and occurs in the continental margin arc environment. These dykes, together with the Zadoi arc, the Jiangda- Weixi arc and the Yunxian arc, are the products of the subduction of the Paleo- Tethys main ocean basin, thus forming an arc magmatic belt with a length of tens of thousands of kilometers.