Holey tungsten oxynitride nanowires are vertically aligned on carbon nanotube fibers and applied as negative electrode of high performance supercapacitor. Due to the rich nitrogen doping and holey structure, this negative electrode displays an excellent electrical conductivity, a high volumetric capacitance of 265 F cm(-3) at 0.08 A cm(-3) and a good capacitance retention of 94.15% after 20000 cycles at 1.0 A cm(-3). When it is applied in an asymmetric flexible fiber-shaped supercapacitor matched with a manganese-based positive electrode, the device achieves a remarkable volumetric capacitance of 52 F cm(-3) at 0.5 A cm(-3) and an extraordinary volumetric energy density of 23.4 mW h cm(-3) at 0.45 W cm(-3) with a maximum working voltage of 1.8 V. Therefore, this simple fabrication of stable negative materials opens a new pathway for application of high energy density asymmetric fiber-shaped supercapacitor in new generation flexible energy storage devices.