Abstract: The chemical compositions of magmatite reflect the material source and the tectonic background,especially the content and distribution of microelements.By means of analyzing and processing typical Meso-Cenozoic volcanic rocks in the northern Erlian basin,it is considered that the Mesozoic volcanic rocks are dominated by alkalibasalt,the light rare earth elements concerntrate relatively and come out continent plate surrounding;And the magma of Cenozoic volcanic rocks come from deep crust and they form in rift-valley of continent.It presents basic material to research the formation and evolution of the Erlian basin.