One-dimensional porous Co3O4 nanowires with different length have been successfully synthesized by thermal decomposition of Co-NA polymer precursors at various hydrothermal reaction times. The positive effects of longer nanowires and larger surface area on electrochemical performance of Co3O4 samples were investigated systematically. All the as-prepared Co3O4 samples display excellent discharge capacities and cycle stability on account of large surface area and porous structure, indicating great potential application of porous Co3O4 nanowires for alkaline rechargeable batteries. The Co3O4-24 h sample with the longest length shows the most outstanding electrochemical performance, and displays the maximum discharge capacity of 450.1 mAh g−1 with the capacity retention of 90.4% after 100 cycles at a current density of 100 mA g−1. Electrochemical reactions between Co and Co(OH)2 occurring on the Co3O4 electrodes are investigated by XRD, cyclic voltammetry (CV) and charge–discharge measurements.