In　order　to　accurately　compute　the　axial　stiffness　of　bolted　members,　the　compressive　stress　of　each　compressive　section　perpendicular　to　the　bolt　axis　is　assumed　as　a　quartic　equation　of　the　radial　size.　Following　this　assumption,　new　formulas　for　member　stiffness　are　derived.　Finite　element　analysis　and　its　interpolation　algorithms　are　conducted　to　calculate　the　stiffness　of　members　with　different　materials　and　geometrical　sizes.　The　obtained　member　stiffness　is　used　to　inversely　calculate　the　corresponding　semi-apex　angle.　Moreover,　the　real　semi-apex　angle　is　obtained　from　the　contact　pressure　data　of　the　member　interface　which　is　measured　with　the　I-Scan　system.　The　experimental　results　show　good　coincidence　with　the　analytical　semi-apex　angles,　and　the　corresponding　error　is　within　2°.　On　the　basis　of　the　above　derived　formulas　for　the　semi-apex　angle　and　the　member　stiffness,　the　axial　stiffness　is　calculated　for　bolted　members　with　different　materials　and　geometrical　sizes.　Compared　with　the　finite　element　analysis,　the　errors　of　obtained　member　stiffness　get　less　than　6%,　so　the　member　stiffness　can　be　accurately　calculated　with　the　proposed　method.