Objective:To establish a technique of marking the position of atlas pedicle screw entry point with the medial border of axis pedicle as an anatomical landmark. Methods:100 atlantoaxial CT films of normal adults(including 50 males and 50 females)were selected randomly to measure the horizontal distance from atlas pedicle screw entry point to medial border of axis pedicle by Tan’s method(method a)and Ma Xiangyang’s method(method b). The reliability of using the horizontal distance for marking the positioning of atlas pedicle screw entry point through clinical application was evaluated. Results:In method a,the horizontal distance was(6.0 ± 0.8) mm in male,and(5.5 ± 0.8) mm in female. In method b,it was(9.4 ± 1.1) mm in male,and(8.2 ± 1.3) mm in female. 8 atlas pedicle screws were placed exactly in 4 patients,and no neural or vascular injury was observed. The postoperative radiographs verified all of atlas screws with a good position. Conclusion:The medial border of axis pedicle could be as a convenient anatomic landmark to determine the position of atlas pedicle screw entry point,and the landmark is more invariant and clear comparing with the previous anatomical ones.