Polyimide-based triboelectric nanogenerators (TENGs) capable of energy harvesting in harsh environments (high temperature and high humidity) have been extensively studied. However, most polyimide-based TENGs have the disadvantages of poor air permeability and poor softness. In this study, a core–shell yarn with good air permeability, softness, and high electric output performance was successfully prepared by conjugate electrospinning. FEP-doped FPI and nickel-plated aramid yarn were employed as the shell and core materials, respectively. Due to the unique hierarchical porous structure and fluorinated functional group modification, the yarns exhibit excellent output performance (maximum open-circuit voltage is 22.7 V per length of 10 cm) compared to traditional polyimide yarns. The textile woven with this yarn has good high-temperature resistance, antifouling, waterproof, and self-cleaning performance, and still maintains an output performance of about 80% under 99% relative humidity. Moreover, this textile-based TENG has no significant attenuation after 10,000 cycles, showing good stability and durability. Finally, the TENG based on the intelligent fire suit is designed, which can be used for the movement and position monitoring of firefighters in high-temperature and high-humidity environments. This fluorinated polyimide yarn prepared in this study provides a promising solution for the development of self-powered sensors capable of monitoring the movement status and position of firefighters in high-temperature and high-humidity environments.