Abstract: The mechanical properties of the carbon fiber reinforced epoxy composite pyramid lattice sandwich prosthetic foot structure under vertical load were studied. Three kinds of prosthetic feet with different relative densities were prepared and subjected to vertical load compression test. The results show that the relative density has a significant effect on the mechanical properties of the structure. The load-displacement curve is nonlinear. The peak load and stiffness values increase with the increase of the relative density. The three failure modes of relative density are node failure and panel wrinkling. Curves and structures have a certain energy absorption capacity. The theoretical strength prediction model of the pyramid lattice sandwich prosthetic foot structure was established, and the deflection response of the structure under the vertical load was given. Four failure modes and critical failure loads were obtained. Comparing the peak load, failure mode and deflection of theoretical calculation and experiment, a good consistency is obtained. The effect of the structural parameters of the prosthetic foot (thickness of the panel, angle of the rod and diameter of the rod) on the failure mode and the critical load of the failure were given, and the structural failure mechanism diagram was drawn.