Abstract: The age of the Tuchengzi formation in Northern Hebei and Western Liaoning provinces has long been disputed. There are mainly five viewpoints: 1) late Middle Jurassic to early Late Jurassic; 2) early Late Jurassic; 3) Late Jurassic; 4) Late Jurassic to Early Cretaceous; and 5) Early Cretaceous. Based on biostratigraphy, magnetostratigraphy, isotopic dating as well as current situation of the Jurassic chronostratigraphic studies, the age of the volcanic rocks of Tuchengzi formation is dated 147 -136 Ma, i.e. the late of Middle Jurassic to the early of Late Jurassic (CallovianOxfordian).