A novel nanosensing system was constructed for highly sensitive and selective detection of cysteine (Cys) via the combination of the excellent optical properties of bovine serum albumin-stabilized gold nanoflowers (BSA-AuNFs), the high selectivity of the molecular structure regulation performance of cystine, and the high sensitivity of the multi-cascade signal amplification strategy. The sensing mechanism has been confirmed by UV-vis absorption spectroscopy, TEM, HRMS and