The problems of no energy dissipation under small earthquakes and large residual displacement under large earthquakes are the pain points of traditional metallic dampers. To address this issue, a self-centering dual-stage yield U-shaped metallic damper (SC-DYUMD for short) with asynchronous activation and parallel dual-yield characteristics was proposed. This damper exhibits significant dual-stage yield performance and excellent self-centering capability.Based on the structure and working principle of SC-DYUMD, the restoring force model is derived, and the dual-stage characteristics and the inherent mechanism of self-centering are revealed. Low-cycle reversed displacement loading simulations were conducted on 16 groups of SC-DYUMD specimens. The effects of combined disc spring preload and U-shaped plate width on the performance of SC-DYUMD were studied, and a reasonable range of design parameters was provided. The research results show as follows. SC-DYUMD can effectively dissipate energy under earthquakes of different intensities, and the initial gap of the long circular hole endows it with significant dual-stage energy dissipation characteristics; when the width of the U-shaped metallic damper plate increases from 80 mm to 140 mm, the energy dissipation capacity is increased by up to 20.10%. When the preload increases from 80 kN to 200 kN, the residual deformation rate is reduced by up to 99.42%. The coupling effect of combined disc spring preload and U-shaped plate width enables SC-DYUMD to still maintain excellent energy dissipation and self-centering capabilities after experiencing earthquakes. It is recommended that the initial preload be controlled within the range of 160~200 kN and the width of the U-shaped plate be controlled within the range of 100~120 mm to achieve optimal performance.