Objective To study the mechanical response of the distal tibial cancellous bone and the tibial prosthesis after the radial and axial functionally graded materials (FGM) were implanted into the ankle joint. ? Methods Using three functional gradient materials, titanium alloy-bioactive glass composite functional gradient material (FGM-I) , titanium alloy-ideal bone elastic composite functional gradient material (FGM-II) and a titanium alloy-hydroxylapatite composite functional gradient material (FGM-III) . A three-dimensional finite element model of total ankle arthroplasty was established, and a simulation software Abaqus was developed based on Fortran. By changing the volume fraction, the mechanical properties of the functional gradient tibial prosthesis were adjusted both axially and radially. To analyze the stress distribution of tibial component and cancellous bone after FGM axial tibial component and radial tibial component implantation in standing position. Results? Compared with ti-alloy tibial prosthesis, three kinds of FGM can effectively reduce the stress concentration on the tibial prosthesis, and the overall effect of FGM-III tibial prosthesis is better than that of FGM-I and FGM-II tibial prosthesis, the radial distribution of FGM can effectively reduce the maximum Von Mises stress of the prosthesis. For cancellous bone of tibia, three kinds of FGM radial tibial prostheses and FGM-III axial tibial prostheses can effectively increase the distal stress, thus relieving the stress occlusion on cancellous bone, FGM-III radial tibial prosthesis was the most effective in improving the stress level of cancellous bone. Conclusion? FGM ankle prosthesis can reduce the stress shielding effect and prolong the life of the prosthesis, which has a potential application prospect.