Abstract: Taking a group of steel plate shear wall(SPSW) with openings with or without edge members as example, this paper states the importance of edge members in view of initial stiffness, ultimate load and ductility.The reasonable stiffness value of edge member in SPSW with opening become the key to the problem, for inedquate stiffness makes anchorage of plate too weak to produce effective tension zone to consume energy while excessive stiffness will attract excessive seismic force, bringing adverse effect to structure.In order to get the reasonable stiffness range of edge members, stating with minimum inertia moments, this paper finds out from examples that initial stiffness changes geatly when the inertia moments ratio ranges from 6 to 8, which represents not only adequate anchorage from edge member stiffness, but also direct loading with main frame.Thus this range includes the optimal stiffness of edge members.To prove the rationality of the stiffness range deeply, analysis of expanding the aspect ratio of SPSW is carried out and results states that provided the stiffness of edge member locates in the reasonable range, the ultimate load increases apparently, while the ductility also increases slightly.