Fiber/wearable power devices such as fiber solar cells, fiber nanogenerators, and fiber thermoelectric devices have incomparable advantages in building flexible portable electronics. Wearable energy supply products are particularly highly flexible and adaptable to arbitrary installation circumstances. However, studies on such power devices mainly focus on energy conversion, and the development of fiber electronic devices for energy storage continues to lag. Herein, we demonstrate a novel type of flexible fiber/wearable supercapacitor that is composed of two fiber electrodes, a helical spacer wire, and an electrolyte. Additionally, we directly utilize low-cost commercial pen ink as the electrochemical material to produce a carbon-based fiber supercapacitor (FSC) with high areal capacitance (19.5mF/cm2) and high power. The electrochemical activity of the FSC remains stable after 15,000 cycles. FSCs are beneficial in achieving low-cost, large scale, and efficient flexible/wearable energy storage systems.