A　reticulated　shell　is　one　of　the　conventional　long-span　space　structures,　prone　to　progressive　collapse　under　a　severe　earthquake　because　of　its　unique　single-layer　feature.　However,　the　collapse　mechanism　of　this　type　of　structure　has　not　been　well　studied.　In　this　paper,　a　numerical　modeling　technique　using　the　fiber　beam　elements　is　developed.　A　corresponding　material　model,　based　on　the　inclusion　of　damage　accumulation,　is　also　developed　in　order　to　determine　the　failure　criteria　of　structural　members.　An　effective　way　to　simulate　the　buckling　behavior　of　the　structural　members　is　also　used　in　the　numerical　simulation.　The　relevant　numerical　method　is　developed　and　validated　against　experimental　tests:　good　agreement　is　achieved.　Based　on　this　numerical　method,　a　parametric　study　of　the　reticulated　shell　under　severe　earthquake　loading　is　performed,　the　responses　of　the　structure　are　investigated,　and　a　three-stage　collapse　mechanism　of　this　type　of　structure　is　observed.　(c)　2018　American　Society　of　Civil　Engineers.