The polyaniline/hydrothermal active carbon fiber (PANI/EACF) is designed and acted as supercapacitor electrode for the electrochemical energy storage application. PANI fiber layer with porous structure is fully covered on the surface of EACF substrate to form electroactive PANI/EACF electrode. The active carbon fiber (ACF) conducts the electrochemical oxidation and reduction activation to form EACF with functional hydroxyl group. The PANI/EACF with intermolecular hydrogen bond interaction exhibits the stronger and more stable bonding interface than PANI/ACF with Van der Waals force interaction, which accordingly promotes the interfacial charge transfer and charge storage capacitance in the charge–discharge process. PANI/EACF exhibits higher response current density than PANI/EACF at the same scan rate, indicating higher conductivity and electroactivity of PANI/EACF. The specific capacitance declines from 78.1 to 36.8 F g−1 for PANI/ACF and from 133.5 to 65.3 F g−1 for PANI/EACF when current density increases from 1 to 10 A g−1, presenting the obviously improved capacity. The corresponding capacitance retention, respectively, achieves 47.1 and 48.9%, presenting the slightly increased rate capability. The capacitance retention ratio of PANI/ACF and PANI/EACF achieves 61.4 and 67.1% at 5 A g−1 after 1000 cycles, presenting the slightly increased cycling stability. PANI/EACF with superior capacitive performance in the electrochemical charge–discharge process presents the promising energy storage application.