Abstract: As a combined yielding-type metal damper, the U-shaped steel plate damper is composed of U-shaped plates, connecting plates and anchoring devices. The multi-dimensional hysteretic behaviors of the U-shaped steel plate damper were studied in this paper. The hysteretic behaviors of the U-shaped steel plate damper under uni-directional in the horizontal, vertical and out-of-plane horizontal directions were investigated by pseudo-static tests, respectively. Simplified calculation formulas for the force-displacement relationship of the U-shaped steel plate damper in the horizontal, vertical and out-of-plane horizontal directions were developed, respectively. The hysteretic behaviors of the U-shaped steel plate damper under multi-directional loading were further explored through the solid finite element model. The research results show that under uni-directional loading, the deformations of the U-shaped plate in the horizontal direction and out-of-plane horizontal direction are concentrated at the junction of the straight section and the arc section, and the hysteretic curves are symmetrical. In the vertical direction, the deformation is concentrated in the middle of the arc section, and the hysteretic curve is asymmetric. Under multi-directional loading, the deformation of the U-shaped plate is not confined to a singular localized region but instead manifests as a complex combination of bending, torsion, tension, and compression across its entire structure. In addition, the strengths of the U-shaped plate in the horizontal and vertical directions are greater than that under uni-directional loading, and the hysteretic curves in the horizontal and vertical directions of the U-shaped plate are also asymmetrical, while the hysteretic curve in the out-of-plane horizontal direction is similar to that under uni-directional loading. The yield strength, initial stiffness and energy dissipation capacity of the U-shaped steel plate damper increase significantly with the increase of the thickness t, and decrease with the increase of the radius R of the arc section.