Abstract: In the area of Yangyuan, Weixian and Huai’an, Hebei, there occurs a suite of grayish-white and red sandy conglomerates and argillites, named the Huiquanbao Formation, which was formerly assigned to the Eocene. The author et al. （1982） conducted field work in this area and discovered an abundance of Hadrosauridae and Pliosauridae in the middle and lower parts of the Huiquanbao Formation and the ostracod fauna represented by Mongolianella-Cypridea and the charophyte flora represented by Maedlersphaera corollacea-Euaclistochara of. mundula in its upper part. This paper discusses the age of the biotas, and a correlation was made between these biotas and those in relevant areas. This discovery not only enriches the content of the association of late Mesozoic biotas in northern China and determines the geologic age of the Huiquanbao Formation to be late Cretaceous, but also is of major significance for the study of late Mesozoic biotas and stratigraphy.