Comparative study was carried out on the Cretaceous OAEs discovered in China. The results show that the carbon isotope of the leaf wax from the highland of the Luanping basin, Hebei province, is positive excursion, which probably responded terrestrially to the Weissert Anoxic Event. It is suggested that the Weissert OAE is a global, not local event. There are two mechanisms responsible for carbon isotope positive excursion of leaf wax: one during the early Cretaceous reflects CO2 increase in atmosphere, and the other during the late Cretaceous was caused by terrestrial ecosystem change.