Abstract: The volcanic rock association which formed during Sinian to Cambrian period in the Tarim microplate can be divided in to alkaline basalt,tholeiite and rhyolite1 Based on the studying of trace elements and REE geochemical characteristics for the basalt,we have come to some conclusions that the volcanic rocks mainly formed in continental rift valley,but their source region were affected by the contents which derived from the subduction oceanic crust.These geochemical information is significance to discuss about the evolutionary process and the tectonic setting during Sinian to Cambrian period in Tarimarea.