Based　on　a　scale　model　experiment　on　a　Kiewitt　single-layer　spherical　latticed　shell　structure,　mode　localization　phenomenon　is　studied.　The　quantitative　description　index　of　mode　localization　is　defined.　Several　variation　cases　of　physical　parameter　are　constructed　by　additional　node　mass　and　weakening　member　cross-section　in　the　experiment.　Modal　tests　are　done　on　the　structures　under　each　case　by　the　high-accuracy　method　of　experimental　modal　analysis.　Three　structural　modals　are　tested　and　obtained　at　random,　and　the　variation　and　localization　of　the　three　modes　under　each　case　are　analyzed.　The　results　show　that　the　slight　variation　of　structural　physical　parameter　is　likely　to　make　some　modes　change　and　localize　obviously.　So　the　influence　from　mode　localization　should　be　considered　for　earthquake　resistance　calculation　and　the　damage　identification　of　lattice　shell　structures.