Moisture-enabled electricity generation as an emerging new energy-harvesting technology is one of the most fascinating and promising candidates for supplying renewable and clean power. However, existing moist-electric generators (MEGs) can only produce intermittent, brief bursts of power with voltage output less than 1 V, severely restricting their practical applications. Therefore, there is an urgent requirement for next-generation MEG devices with high efficiency and continuous energy harvesting properties. In this work, an ion-gradient-enhanced MEG consisting of electrospun nanofiber fabric and porous active electrode was demonstrated to provide a perfect solution for solving instantaneous and low electric output at the same time. The assembled MEG can produce a sustained voltage output of 1.1 V for 40 000 s without any weak signs, reaching the highest level among all reported MEGs. This remarkable performance mainly arises from the higher concentration difference induced by the introduced active electrode which enhances ion diffusion through the porous nanofiber fabric. In addition, the co-existing streaming potential also contributes to the excellent performance. Beyond power generation, the electrospun nanofiber based MEGs also demonstrate successful applications in self-powered sensors, including ammonia leak monitoring and moisture-temperature sensor for forest-fire detection. This study provides insights for the designing of innovative MEGs and opens a pioneering avenue for future energy conversion.