Objective：To establish three dimensional finite element analysis（FEA） model of single external fixation screw penetrating into tibia shaft. Methods：Softwares of Mimics，Pro/E，Geomagic Studio，Ansys Workbench13 were used to set up FEA model of tibia-screw assembly successfully；results after applying force and moment loads were observed. Results：The shaft of tibia and single exter－nal fixation screw generated 3 710 volume meshes，6 952 nodes. Von-Mises stress and Total Deformation revealed the maxium stress of the screw and total deformation were located at contact surface and screw tail respectively. Conclusions：Three dimensional tibia-screw assembly model can provide basis for quantitative studies of stresses of the screw and the tibia as well as for biomechanical study of screws made by different materials and with different loads.