Abstract: Middle Jurassic-Early Cretaceous volcanic rock are widely distributed in Baiyunzhang volcanic eruptive basin of Dongguan-Huidong region of eastern Guangdong,where a suite of alkalic volcanic rock in upper part,mainly composed of alkali-feld-spar rhyolitic-trachytic pyroclastic rocks was discovered.In light of petrology,mineralogy,petrochemistry,petrogeochemistry,isotopic age and contact nature,the suite is named Baiyunzhan Formation.It lies between the Late Jurassic-Early Cretaceous Nanshancun Formation and lower part of the Early Cretaceous Guancaohu Formation,belonging to Late Jurassic-Early Cretaceous in age.