As　a　key　bearing　member　of　stretch　forming　lattice　structure　(SFL),　the　upper　chord　ring　beam　is　a　cross　center　of　all　radiating　upper　chord　beams.　In　order　to　deeply　understand　the　displacement　character　of　SFL　affected　by　upper　chord　ring　beam,　six　mechanic　models　about　SFL,　whose　rigidity　are　monotone　increasing,　are　established　on　the　basis　of　ANSYS　finite　element　program,　which　selects　two　tensioning　method-tensioning　simultaneously　step　by　step　and　tensioning　group　by　group　and　step　by　step.　So　the　displacement　rule　affected　by　upper　chord　ring　beam　is　concluded.　When　the　construction　method-tensioning　group　by　group　and　step　by　step　is　chosen,　the　overstepping　or　lagging　displacement　on　structural　nodes　belonging　to　different　group　inevitably　comes　into　being,　which　is　different　from　the　method　of　tensioning　simultaneously.　The　study　shows　that　properly　reinforced　upper　chord　ring　beam　will　weakens　the　displacement　difference　in　a　great　extent,　and　it　is　favorable　to　SFL　forming.