Abstract: In this paper,the Cretaceous in the Tuoli-Dahuichang area,Western Hills, Beijing,is lithos-tratigraphically divided in ascending order into the Donglanggou Formation,Dahuichang Forma-tion,Tuoli Formation and Xiazhuang Formation,It expounds the theory and grounds for rejectingthe Xinzhuang Formation and disintegrating the Lushangfen Formation。Besides,it is confirmedthat the Donglanggou Formation is represented by an association of pyroclastic rocks,sedimentaryrocks and basalt.The isotope ages of 105. 3±2.71Ma and 100.14±2.35 Ma were obtained for thefirst time.