Abstract: In order to study the diagonal channel stiffened steel plate shear wall (SPSW) with a large span-to-height ratio, three 1/3-scaled SPSW specimens were tested under cyclic quasi-static loading. One of the specimens was spliced SPSW without diagonal channel stiffeners and the other two were spliced SPSWs with diagonal channel stiffeners. The experimental results show that SPSWs have good energy dissipation capacities, and the hysteretic curves of the diagonally stiffened SPSWs are plump spindle-shaped. The closed section formed by the channel stiffener and the plate avoids the torsion of the stiffener during the loading process. Channel stiffeners can increase the elastic buckling load and limit the out-of-plane deformation of the infill plate in the elastic stage. Moreover, diagonal stiffeners improve the bearing capacity of the specimen in elastoplastic stage. The formulas for calculating the shear force, axial force and bending moment of the frame column are derived. The results show that the axial force and shear force of the columns are greatly affected by the diagonal channel stiffeners, thus the supporting effect of the stiffener should be considered in the design.