Abstract: Objective To establish a finite element model of occipitoatlantoaxial complex and analyze the role of atlas ring integrity in maintaining the distance between occipital bone and axis. Methods A finite element model of occipitoatlantoaxial complex consisting of bones,ligaments and joints was established and verified by comparing cadaver experimental data.Models simulating different partial transection of atlas ring were loading under vertical compression.Relation between lateral masses displacement and occipitoaxial compression,displacement severity and different partial transection were evaluated. Results The model correlated cadaver data in most loading modes.With applied 60 Newton vertical load,the lateral masses horizontally separated 0.79mm in model with transection both anterior and posterior arch（AT_PT） and 0.04mm in intact one,resulting in 0.91mm and 0.46mm reduction in occipitoaxial vertical distance.With applied 0.9mm vertical load,the maximum lateral masses separation occurred in the model with transection of both anterior and posterior arch（AT_PT）,followed by anterior arch transection（AT）,posterior arch transection（PT）.The minimum occurred in the model with only inferior portion of anterior arch transection（part AT）.The lateral masses separation was obvious in the model with complete anterior and posterior arch resection（AT_PT） than in the one with anterior（only inferior portion） and posterior arch resection（part AT_PT）. Conclusion Atlas ring continuity should be maintained during surgery since secondary basilar invagination may occur after operation.