Fiber supercapacitors have attracted public attentions because of their merits of relatively high capacitance density, flexibility and easy integration with various electronic devices. In this work, a flexible coaxial-type fiber solid-state asymmetrical supercapacitor (ASC) based on Ni3S2 nanorod array electrode and pen ink electrode was successfully fabricated. The Ni3S2 nanorod array electrode was synthesized by directly growing Ni3S2 nanorod arrays on a nickel wire through a facile hydrothermal method and the pen ink electrode as negative electrode was synthesized by a simple dip-coating method. The solid-state ASC device presents a stable voltage window of 1.4 V and behaves a high specific capacitance of 34.9 F g−1 (87.25 F cm−1) at a scan rate of 10 mV s−1. Compared with the symmetric supercapacitor (SSC) based on Ni3S2 electrodes, the ASC device provide an increased energy density of 8.2 Wh kg−1 (0.81 mWh cm−3) at the power density of 214.6 W kg−1 (21.12 mW cm−3). In addition, the ASC device also exhibits excellent electrochemical stability with 93.1% of initial specific capacitance after 3000 consecutive cycles and good mechanical stability. These encouraging results present its great potential in flexible solid-state energy storage devices.