To enhance the bonding strength between the active material and the core yarn current collector through nano-entanglement, bacterial cellulose/carbon nanotube (BC/CNT) nanofiber yarns were developed using in situ cultivation and wet twisting. This method utilizes the large specific surface area and abundant active functional groups of BC-based nanofibers. Subsequently, V2O5/BC/CNT composite yarn electrodes were fabricated, exhibiting a core-sheath structure with excellent conformal characteristics. The influence of ultrasound duration on the conductivity and electrochromic performance of composite yarns was investigated. The initial discharge-specific capacity was recorded as 105.3 mAh/g, with a capacity retention rate of 60.2% after 100 cycles. The composite yarn exhibited 100 reversible transitions between yellow and blue, with reduction and oxidation response times of 2.35 s and 3.3 s, respectively. The modulation amplitude at 532 nm during the initial cycle was 20.31%, and after 100 cycles, the modulation amplitude retention rate remained at 68%.