Cable-strut　tensile　structures　(CSTS)　are　mainly　composed　of　cables,　and　the　cable　length　errors　are　bound　to　exist　in　the　manufacturing　of　cables.　The　cable　length　errors　have　significant　impacts　on　the　mechanical　properties　of　CSTS　under　load　effects.　Meanwhile,　CSTS　generally　uses　flexible　membrane　material　as　roofs,　therefore　cable　length　errors　will　result　in　the　wrinkle　of　roofs　and　then　cause　the　secondary　accumulation　effects　of　rain　and　snow　load.　Therefore,　it　is　necessary　to　reasonably　control　the　manufacturing　errors　of　cable　length.　In　order　to　solve　the　problem,　the　method　of　solving　the　control　limits　of　cable　length　errors　of　CSTS　is　proposed　due　to　the　prestressed　relaxation　under　load　effects.　The　reliability　index　of　CSTS　is　firstly　given　based　on　the　reliability　theory.　Then,　based　on　the　reliability　index　and　the　criterion　of　prestress　relaxation　under　load　effect,　the　critical　state　equation　and　constraint　inequality　group　are　constructed,　and　the　coefficient　matrix　of　constraint　inequality　group　is　derived.　Meanwhile,　the　nonlinear　finite　element　method　for　solving　the　coefficient　matrix　of　constraint　inequality　group　is　proposed.　The　procedure　of　solving　the　control　limits　of　cable　length　errors　of　CSTS　is　given　based　on　the　proposed　method.　The　crossed　spoke　cable-truss　structure　is　taken　as　an　example　to　verify　the　feasibility　of　the　new　method.　The　research　contents　provide　an　effective　solution　for　controlling　cable　length　errors　of　CSTS　for　prestressed　relaxation　under　load　effect.　©　2023　Institution　of　Structural　Engineers