Objective To investigate the feasibility of absorbable magnesium alloy screws in atlantoaxial dislocation fixation. Methods Four kinds of screws with triangular, rectangular, trapezoidal and zigzag screw thread were designed with WE43 magnesium alloy. The finite element simulation analyses were performed on the screw- polyurethane model and atlantoaxial fixation system model. The stress and displacement distributions on the models were obtained. Results The pull-out force simulations were carried out on four kinds of magnesium alloy screws according to ASTM F 543. The results show that the peak stress on the screw with triangular thread is the smallest, and that on the screw with zigzag thread is the largest. The magnesium alloy screw with triangular thread has good fixation effect on atlantoaxial dislocation. Hydroxyapatite (HA) coating on the surface of screw with triangular thread can reduce the peak stress of the screw. Conclusions Under the same loading condition, the screw with triangular thread has good stability and the best pull-out force performance. After heat treatment, the strength of magnesium alloy screw with triangular thread meets the load-bearing requirements for atlantoaxial dislocation fixation. HA coating on the screw surface can optimize the mechanical properties of screw, and there is a good bonding strength between the coating and the screw.