Porous　design　of　orthopaedic　implants　affords　the　advantages　of　minimizing　stress　shielding　and　improving　the　osseointegration　and　long-termstability.　However,　the　marked　error　in　the　manufactured　porous　structure　relative　to　the　designed　model　yields　limited　application　of　the　porous　design.　This　study　aimed　to　develop　a　methodology　to　derive　the　relationship　between　the　porosity,　the　structural　characteristic　parameters　and　the　mechanical　properties　of　a　typical　structural　unit,　to　lay　the　foundation　of　a　porous　structural　design　for　3D-printed　implants　with　gradient　modulus.　Mathematical　expressions　related　to　porosity　were　determined　based　on　various　parametrical　characteristics　of　porous　units;　the　effective　modulus　of　such　a　porous　structure　was　studied　under　variable　axial　loading　by　using　finite　element　analysis　to　gain　insight　into　the　anisotropic　properties　of　the　porous　structure,　and　to　evaluate　the　effects　of　parametrical　variation　on　the　aforementioned　properties.　For　validation　purposes,　samples　were　manufactured　via　selective　laser　melting　(SLM)　3D　printing　technology　and　mechanically　tested.　Results　indicated　that　porous　design　can　reduce　the　effective　modulus　of　implants　by　75-80%.　A　general　methodology　was　developed　for　evaluating　BCC　structural　units　to　determine　design　parameter　correlations,　the　porosity　and　the　effective　modulus　of　the　structure.　(C)　2017　Published　by　Elsevier　Ltd.