Electroluminescent electronics with flexible and lightweight have garnered significant attention in the community of smart textiles. However, current electroluminescent devices mainly depend on petroleum-based matrices, complex high-voltage power supplies, and embedded sensors, limiting their suitability for sustainable, lightweight, and visually intuitive wearable electronics. Here, a flexible, high-luminance silk-fibroin-based alternating current electroluminescent fiber (SFELF) with a coaxial structure is fabricated via conjugate electrospinning, coating, and wrapping techniques. By precisely engineering the luminescent layer matrix with silk fibroin and adjusting its β-sheet-rich secondary structure, the resulting SFELF exhibits outstanding mechanical toughness (5.29 MJ m−3) and high luminance (up to 366 cd m−2), outperforming reported counterparts based on polydimethylsiloxane and cellulose matrices. Notably, this fiber maintains stable brightness after more than 10 000 bending cycles, suggesting its superior mechanical durability and stability. Furthermore, even after the structural outer electrode is removed, the fiber retains its sensitive touch-activated luminescence performance, which can be modulated by external electric or thermal fields without the need for an external power supply. This luminescence phenomenon can be achieved by touching with finger or metal materials. Regarding potential smart textile applications, SFELF integrates triboelectric and liquid sensing capabilities, enabling real-time visual monitoring and offering great potential for human–machine interaction.