Abstract: In the assembled steel buckling-restrained brace (ABRB), the restraining part is formed by several outer parts around its core. Therefore the connection design of the outer restraining parts is a main focus in the overall design theory of ABRB, and this feature is quite different from that of the traditional BRBs which have an outer overall restraining part around the core. A simplified design method has been proposed to determine the bolt forces in a four-angle ABRB, but it is only fit for the situation that the outer restraining parts bends in one direction. Firstly, this paper presents the numerical results to verify the simplified design method already obtained, and the method is modified accordingly. Secondly, the gap between the core and the outer restraining parts makes BRB deform normally in two directions, therefore this paper also aims to determine bolt forces for the more general situation. The approach proposed in this study is to combine the bolt forces selectively, which are induced by the BRB’s bends in each direction. Finally an improved connection design method for the four-angle ABRB is achieved.