Objective To predict the stress distribution of atlas under different pre-trauma postures by finite element method, and to deduce the sites of atlas fracture accordingly. Methods To set up the three-dimensional geometrically and mechanically finite element model and analyze the stress distribution of atlas under three different pre-trauma postures. Results In neutral posture, the high stress distribution occur at anterior arch and the junction between the posterior and lateral mass; in flexion posture, the high stress distribution occur at anterior arch;in extension posture, the high stress distribution occur at anterior arch and the junction between the posterior and lateral mass. Conclusion Since the high stress usually occur at the junction between the anterior arch and anterior nods, the junction between the anterior arch and lateral mass, and the junction between the posterior and lateral mass, these sites of atlas are likely to be the fracture sites. The type and sites of atlas fractures are highly dependent on the force vector applied to head, head posture at the time of trauma, atlas geometry and physical properties.