There has been different understanding of geological natures of the Gangdese belt in Tibet during the Paleozoic. This paper presents the data of geochemistry and UPb dating of Yawa mafic complex exposed in Dajiacuo area, southern Gangdese so as to put constrain on this issue. A weighted average age of one clinopyroxene sample from the Jawa mafic rock is 263.5±4.0Ma (MSWD=0.34) and the ages of two gabbro samples are 263.9±2.4Ma（MSWD=0.38） and 262.7±2.3 Ma（MSWD=2.8）respectively, revealing that the Permian plutonism existed in the Gangdese belt. Two kinds of rocks in the Yawa complex belong to alkaline rock series characterized by high content of TiO2, and are different from island-arc volcanic rocks in the Gangdese belt, similar to intraplate basalt. The REE patterns of the samples exhibit enrichment of light REE, with Eu=0.98～1.07. The HSE abundance of the samples is equal to that of intraplate basalt, and the ratios of Zr/Nb and Hf/Th are 3.07～4.94 and 1.25～1.98, respecticely. All this features indicate that the Yawa mafic complex is similar to intraplate basalt. The patterns of chondrite normalized REE and MORB normaized trace element indicate that the Yawa complex developed in a intraplate setting, and this is supported by the trace element identification figure of tectonic setting. Based on the regional sedimentary features, volcanics and deformation and metamorphism during Carboniferous and Devonian, it is suggested that southern Gangdese was in passive continental margin, and northern area in active continental margin during the Devonian.