In　order　to　study　the　mechanical　performance　of　internal　stretch　forming　space　lattice　structure　(ISFSL),　twelve　models　with　different　the　sag-span　ratios　and　rise-span　ratios,　were　found　by　taking　sag-span　ratio　and　rise-span　ratio　as　design　parameters.　Mechanics　performance　about　axial　force,　bending　moment　and　section　stress　of　ISFSL　being　influenced　by　rise-span　ratio　and　rise-span　ratio　was　fully　analyzed　by　using　ANSYS　finite　element　program.　Two　experimental　models　with　a　long　span　of　4.8　m　were　designed　based　on　the　analysis　about　ISFSL,　tensioned　forming　and　static　loading　were　carried　out.　The　characteristics　of　ISFSL　affected　by　sag-span　ratio　and　rise-span　ratio　were　further　studied,　and　the　theoretical　analysis　results　were　verified.　The　study　shows　that　sag-span　ratio　and　rise-span　ratio　are　the　important　factors　which　affect　the　structural　property　of　ISFSL.　Bending　strain　is　the　mainly　mechanics　performance　in　forming　stage　of　ISFSL,　and　the　increasing　compressive　strain　in　axial　is　the　mainly　mechanics　performance　in　loading　stage.　Reasonable　combination　of　sag-span　ratio　and　rise-span　ratio　helps　to　improve　structural　performance　of　ISFSL.