Nylon is the first synthetic fiber material and is widely used throughout the world. However, traditional nylons show limited optical applications as they emit no or weak fluorescence. Herein, a fluorescent nylon-6 is synthesized by utilizing tetraphenylethylene (TPE) carrying two amino groups as coinitiator. The resulting TPE-labeled nylon-6 exhibits reversible thermal-induced fluorescence color change. This unique property arises from the synergistic effect of its chemical structure and conformation. The thermal expansion of the polymer at high temperature induces the phenyl rings of TPE to rotate in a greater extent, which decreases the conjugation of TPE to lead to a blueshift in its fluorescence. The novel fluorescence property of TPE-labeled nylon-6 enables it to find applications in fields like chemosensor and security label.