The damage of reticulated shell structure will arouse structural mode localization. The quantitative assessment index of mode localization is defined. A scale model experiment for mode localization is carried out on a Kiewit single-layer spherical reticulated shell structure, and the features of mode localization are studied. Four cases about structural stiffness’ change are constructed in the experiment, and three structural modals are obtained at random. The localization of the three modes is analyzed under each case. The results show that slight changes of physical parameters are likely to arouse obvious localization of some modes for reticulated shell structure.