A flexible self-charging power system is built by integrating a fiber-based supercapacitor with a fiber-based triboelectric nanogenerator for harvesting mechanical energy from human motion. The fiber-based supercapacitor exhibits outstanding electrochemical properties, owing to the excellent pseudocapacitance of well-prepared RuO2 center dot xH(2)O by a vapor-phase hydrothermal method as the active material. The approach is a step forward toward self-powered wearable electronics.