Abstract: The Frictional Steel Truss Coupling Beam (FTCB) consists of a steel truss beam and a pair of friction dampers located at both ends of the bottom chord. FTCB features a strength-stiffness decoupling mechanism where the yield strength is controlled by the sliding force of friction dampers, while the stiffness is determined by the layout and dimensions of the truss members. Based on this characteristic, by optimizing the layout of truss members, the stiffness of the component can be further improved or materials can be saved. The variable density method in topology optimization is used to optimize the FTCB with a span-to-depth ratio of 2∶1, exploring a more reasonable distribution of web material in a two-dimensional design space. The objective function is set to minimize the volume of the web, and the maximum vertical displacement at the end of the beam is set as a constraint. Geometric reconstruction is performed on the steel truss beam based on the optimization results, and FTCBs with different strengths are designed. The seismic performance of the optimized FTCB is studied through finite element cyclic analysis. The results show that the optimized FTCB exhibits stable hysteretic behavior and saves approximately 68% of steel while maintaining essentially the same stiffness as the original design. The strength-stiffness decoupling mechanism of FTCB is also validated.