Tengchong volcanic activity is divided into the old period (including Plio cene, Early Pleistocene and Middle Pleistocene) and new period (Middle Pleistoce ne—Holocene, in which the activities of the Maanshan, Dayingshan and Heikongsha n Volc anos started to occur. The representative volcanic rocks are basalt, dacitic wel ded tuff, basaltic trachyandesite and trachyandesite, all belonging to a highpotash calcalka l ine volcanic rock suite. Volcanic activities of the Maanshan Volcano, Dayingshan Volcano and Heikongshan Volcano were traced back at lest to the Middle Pleistocene. The magmas evolved f rom trachybasaltbasaltic trachyandesite of the Middle Pleistocene to trachyand esite of the Late Pleistocene—Holocene.They are origined from a comagma source (or magma c hamber).The genesis and evolution of magmas are related to the crustalmantle interact ion and pyroxene crystallization differentiation within the magma chamber. The trend of the magmatic evolution shows that the magmas beneath the magma chamber of the active vol cano in the Tengchong region tends to becom even more alkaline and silicic magmas of trachyte or rhyolite.