The area of Zhejiang—Fujian boundary underwent intense volcanic activities in Late Mesozoic, but have been studied in low degree in the Late Mesozoic volcanic zone of coastal southeast China. Based on comprehensive field investigations and zircon U Pb geochronometry on typical volcanic strata, the writers analyze lithology and lithofacies of the Late Mesozoic volcanic rocks, and propose the geological process of volcanism in this area. Volcanic activities in the study area took place during 143~111 Ma ( with a peak between 143~126 Ma), i.e., Early Cretaceous, in which occurred a long intermission in 126~116 Ma. The volcano sedimentation process can be divided into five stages, which is conducive to understand temporal and spatial evolutions of Early Cretaceous volcanism in coastal Southeast China.