In　actual　engineering,　material　properties,　load　effects,　and　other　factors　of　mechanical　structures　change　due　to　long-term　use.　In　order　to　understand　the　operation　of　a　mechanical　structure　in　real　time,　it　is　crucial　to　obtain　the　dynamic　trajectory　of　its　reliability.　Considering　the　time　variability　of　a　mechanical　structure　over　time,　uncertain　random　variables　are　introduced　to　express　the　uncertainty　of　various　parameters　of　structures,　and　the　Wiener　process　is　used　to　describe　the　strength　degradation　process　of　structures　so　as　to　solve　the　calculation　problem　of　time-varying　reliability　of　mechanical　structures.　Based　on　the　advanced　first-order　and　second　moment　method　(AFOSM),　the　proposed　linearized　Nataf　change　is　used　to　complete　the　transformation　from　related　nonnormal　variables　to　independent　standard　normal　variables　in　order　to　simplify　the　calculation　process　of　reliability　solution　and　solve　the　reliability　calculation　problem　of　random　parameters　subjected　to　arbitrary　distribution.　The　deduced　random　variable　sensitivity　factor　indicates　the　degree　of　influence　of　different　random　variables　on　the　reliability　of　the　mechanical　structure,　providing　a　theoretical　basis　for　the　optimal　design　and　maintenance　of　a　mechanical　structure.　The　proposed　method　is　analyzed　using　the　cantilever　beam　and　compared　with　the　nonlinear　Nataf　transform　and　verified　by　the　Monte　Carlo　simulation　results.　The　results　show　that　the　proposed　method　can　effectively　solve　the　reliability　sensitivity　problem　of　structural　system　strength　degradation.