Biomass-based nanofibers prepared by electrospinning have broad prospects in the field of supercapacitors. In this work, biomass tar-based carbon nanofibers (CNFs) are prepared by electrospinning technology, and the CoNi nanosheets are grown on the surface of CNFs. The obtained electrode materials have a three-dimensional open petal-like nanofiber structure, and the results of the electrochemical performances show that the CoNi@CNF-1 has a specific capacitance of 474.4F g−1 at 0.5 A g−1, an energy density of 65.9 Wh kg−1 and a power density of 250 W kg−1. After 5000 charge-discharge cycles, the CoNi@CNF-1 still maintains 95.4 % of its original capacitance in the three-electrode system. This work provides an important reference for the effective treatment of biomass tar and its application in the field of electrochemical energy storage.