The　value　of　sensitive　factors　in　structural　reliability　analysis　greatly　affects　reliability　calculation　results.　These　factors　must　be　accurately　determined　and　studied　to　improve　the　accuracy　of　calculated　results.　Based　on　the　analysis　of　existing　sensitivity　calculation　methods,　a　new　practical　sensitive　factor　analysis　method　was　put　forward　to　analyzing　sensitive　factors　in　structural　strength　reliability　calculations.　The　dimensionless　sensitive　indexes　of　structural　reliability　were　defined　in　the　new　method　to　compare　the　influence　degree　of　random　parameters　to　reliability.　And　the　method　was　applied　to　analyze　sensitivity　under　the　two　conditions　of　the　structural　resistance　decreasing　and　not　changing　with　time.　Random　variables,　defined　by　their　probability　distribution　and　corresponding　distribution　parameters,　were　used　to　describe　uncertainties　in　the　reliability　calculation.　Different　forced　state　RC　columns　were　taken　as　examples　to　analyze　the　structural　sensitivity,　and　sensitive　factors　affecting　the　columns＇　structural　reliability　were　obtained.　The　results　show　that　the　reliability　of　time-varying　structure　has　descended　to　some　extent　compared　with　that　without　time-varying　structure,　and　the　effect　from　the　random　parameters　to　reliability　index.　The　example　and　theory　demonstrate　the　feasibility　and　rationality　of　the　new　method.　This　article　has　certain　reference　value　to　the　structural　design,　construction　and　detection.