Abstract: Current research primarily employs size or shape optimization to enhance the thermo-fluidic per-formance of conventional cylindrical pin-fin cooling systems. However, topology optimization methods can more comprehensively unlock the potential of pin-fin cooling. This study implements level set-based topology optimization on cylindrical pin-fin configurations to improve heat transfer and pressure loss characteristics in cooling channels. Results show that the optimized flow-disruption elements evolve into droplet-shaped structures downstream of pin-fins. These bio-inspired geometries accelerate flow velocity along the streamwise direction while suppressing low-velocity wake regions. Consequently, the Nusselt number demonstrates a monotonic increasing trend along the flow path, and the optimized configuration achieves peak heat transfer intensity with minimal pressure penalty, yielding the best thermo-hydraulic performance.