Three types of cross sectional shapes of struts are designed in a pyramidal lattice truss structure including circular, semi-circular and U-type, and fabricated using pure aluminum by 3-D printing based investment casting technology. The compressive mechanical behaviors of the lattice truss structures were examined and the related mechanisms were analyzed. It is shown that, when the inclination angle was 70°, the compression strengths of semi-circular and U-type lattice truss structures were twice that of circular strut structure due to the increased area moment of inertia of struts contributing to higher buckling resistance.