A high-density array of ZIF-9 was grown on the carbon fiber of carbon paper by a solvothermal method, followed by one-step pyrolysis and reoxidation to form a ZIF-9 based porous carbon/carbon fiber conductive composite material. SEM, TEM, EDS, XRD, XPS, and BET characterization results show that the materials prepared at different oxidation times had the same morphology and composition; With the increase of oxidation time, the pore size shows the tendency of unimodal porous carbon→bimodal porous carbon→unimodal porous carbon. The galvanostatic charge/discharge, cyclic voltammetry, and electrochemical impedance measurements show that the specific discharge capacity and cycle stability of the battery increased first and then decreased with increasing oxidation time. When the oxidation time was 2 h, the prepared C-N-Co3O4(2)/CP material was bimodal porous carbon with the most probable pore diameter of 2.0 nm, and its battery had the best specific capacitance and cycle stability. Porous carbon with suitable pore size and bimodal pores can improve battery capacity and stability.