Abstract: Presents a Spatial-Truss-Confined Buckling-Restrained-Brace (STC-BRB) with shuttle- shape longitudinally, composed of a single steel tube core and the several shuttle-shaped trusses sharing a common external restraining tube. The strength and seismic design of an innovation research in the external restraining system of BRB has being focused on for over a few decades. The STC-BRB could significantly improve the material utilization and particularly enhance the architectural aesthetics when it is exposed externally. The elastic buckling, load resistance, and hysteretic responses of the STC-BRB are investigated numerically by adopting the finite element model (FEM) that has been validated previously by using the test results of Truss-Confined Buckling-Restrained Brace (TC-BRB). And the design method regarding the lower limit of the restraining ratios of the STC-BRBs is recommended. The elastic buckling performance of the STC-BRB is comprehensively investigated by using a beam element FE model, leading to an explicit expression of the elastic buckling load of the STC-BRB that is adopted to define the restraining ratio of the STC-BRB for its structural design. Consequently, the load resistance of STC-BRB under monotonic axial compression is numerically analyzed. Accordingly a lower limit of the restraining ratio of the STC-BRB in their monotonic axial load resistance design is recommended where the core reaches fully sectional yielding with a plasticity strain amplitude reaching 2% without global instability of the STC-BRB. The hysteretic responses of STC-BRB subjected to axially compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of the restraining ratio of STC-BRB is proposed in their energy-dissipating design. These two lower limits of the restraining ratios of the STC-BRB obtained in this study provide fundamentals for the preliminary static and seismic design of STC-BRB.