In　order　to　put　the　internal-prestressed　reticulated　space　structure　through　posttensioning　(IRSSP)　into　practice,　the　paper　firstly　redefined　three　structure　states-zero　state,　initial　state　and　load　state　of　IRSSP.　The　geometrical　displacement　iterative　method　is　then　proposed,　which　is　based　on　the　three　states　mentioned　above.　A　detailed　study　on　the　form-finding　process　is　carried　out　which　based　on　an　IRSSP　with　a　long　span　of　80　m.　The　result　shows　that　the　geometrical　displacement　iterative　method　is　of　high　precision,　great　efficiency　and　the　speed　is　quite　suitable　to　the　form-finding　of　IRSSP.　Furthermore,　the　method　can　ensure　the　integrality　of　the　structure.