<p>The installation of Buckling-Restrained Braces (BRBs) during different construction stages will result in varying initial mechanical states upon bridge completion. To investigate the impact of BRB installation stage on the seismic performance, this study first proposed a nonlinear static-dynamic sequential analysis method capable of precisely simulating the entire cable-hoisting construction process of such bridges. Based on Pushover analysis, the seismic weak positions of the main arch were identified, and a rational BRB layout scheme with key performance parameters was developed using previously developed BRB configurations. Three installation stages for BRBs were then proposed according to the typical construction process of long-span CFST arch bridges, with their impacts on bridge construction stability analyzed and discussed. Nonlinear dynamic time-history analysis was carried out to systematically investigate the influence patterns and mechanisms of BRB installation stage on the seismic performance of long-span CFST arch bridges. The study demonstrates that different BRB installation stages exert minimal influence on the completed bridge’s structural states. However, BRBs installed at various construction stages exhibit significant differences in their own mechanical states upon bridge completion, which substantially affects their energy dissipation capacity during seismic events. BRBs with greater initial axial forces in the completed bridge state demonstrate enhanced total energy dissipation during earthquakes, resulting in more pronounced seismic mitigation effects for long-span CFST arch bridges. This effect amplifies with increasing Peak Ground Acceleration (PGA). Therefore, optimizing installation stage represents a crucial factor in effectively utilizing BRBs for seismic protection of long-span CFST arch bridges.</p>