In　order　to　research　the　relationship　of　load,　damage　and　fatigue　life　for　the　stress　complex　engineering　component,　based　on　the　stress　characteristics　of　titanium　alloy　used　in　the　ships　and　naval　vessels,　the　authors　modified　the　existing　non-linear　continuum　damage　model　according　to　the　fourth　strength　theory,　hence　proposed　the　non-linear　continuum　damage　model　that　conforms　better　to　engineering　practice,　and　estimated　the　model　parameters　according　to　the　uniaxial　fatigue　experimental　data.　By　analysis　of　the　changes　in　material　damage　accumulation　volume　vary　with　changes　of　fatigue　cycles　in　different　fatigue　stress　according　to　the　modified　nonlinear　damage　model,　the　suitability　of　the　proposed　model　was　verified　by　the　SEM　observation　and　analysis　for　the　uniaxial　fatigue　unloaded　specimens.　According　to　the　fatigue　experiments　in　the　stress　complex　state,　through　the　comparison　and　analysis　among　the　results　from　modified　non-linear　damage　model,　the　linear　damage　model　and　the　fatigue　experimental　data　in　the　stress　complex　state,　it　is　found　that　the　linear　damage　model　gives　a　very　much　conservative　estimation　of　the　fatigue　life　within　medium　or　low　load　region;　and　the　modified　model　has　higher　accuracy　and　is　more　consistent　with　the　experimental　data.　Therefore　the　modified　non-linear　damage　model　demonstrates　its　value　in　the　region　engineering　application.