Perovskite/silicon tandem solar cells have emerged as promising candidates for next-generation photovoltaic technology due to their ultra-high power conversion efficiency (PCE)1-3. However, the mechanical stress generated during repeated environmental stress cycles remains a critical challenge for flexible perovskite/silicon tandem solar cells, leading to interfacial delamination and device degradation. In this work, we propose a dual-buffer-layer strategy with a stress-release mechanism to synergistically mitigate ion bombardment during subsequent sputtering deposition and enhance interfacial adhesion while preserving efficient charge extraction. The loose SnO x buffer layer, engineered by adjusting the purging time of atomic layer deposition, can dissipate strain energy, whereas the compact SnO x layer can ensure robust electrical contact. Based on this dual-buffer-layer, the flexible tandem solar cell, constructed on a 60-micron thick ultra-thin silicon bottom cell, achieves a certified PCE of 33.4% on 1-cm2 area, and an certified PCE of 29.8% on wafer-sized area of 260-cm2 with a power-per-weight of up to 1.77 W/g. The modified tandem solar cells demonstrate good durability, retaining over 97% of their initial power conversion efficiencies after 43000 bending cycles under a maximum curvature radius of around 40 mm in air, and around 97% after thermal cycling testing (−40 °C to 85 °C) for 250 cycles.