Abstract: Based on the application of long-span space truss structures, a new type of triple-steel tube buckling-restrained brace was proposed by improving and redesigning current triple-steel tube buckling-restrained braces. The mechanical properties of the brace were analyzed in consideration of initial imperfection. According to this analysis, 4 groups of braces were designed and the effect of strength ratio on the mechanical properties, including the stress state of connection parts, hysteretic behavior, and the failure mode of the core tube, were studied under tension-compression cyclic loading using the ABAQUS software. It is shown that the new structure configuration is feasible and the design method is reasonable. Strength ratio is the key parameter affecting the mechanical properties, and within a reasonable range, the hysteretic performance is well. Under the axial cyclic loading, the effect of inner and outer bushing constraints is obvious, the failure mode of the core tube is multiple-wave small buckling, and the deformation is stably. So the new triple steel tube buckling-restrained brace meets the requirements of design.