The poor cyclic stability of polyaniline restricts its application as an electrode material for supercapacitors, due to the volume changes during the long charge/discharge process. In this work, a thermal crosslinking strategy was developed to improve the cyclic stability of polyaniline electrode materials by thermal treatment of the conventional linear polyaniline (PANI). The heat-treatment conditions including the temperature, atmosphere and time were investigated. Morphology analysis indicated that crosslinked polyaniline (CPANI) had a rougher surface than that of the linear PANI, which could be expected to result in a higher specific area. Compared to the linear PANI, the electrical conductivity of the CPANI increased with the increase of treatment temperature at first and then decreased. The CPANI sample by thermal treatment at 140 °C in air showed the highest electrical conductivity of 6.78 S cm⁻¹. As an electrode material for supercapacitors, the CPANI exhibited an improved electrochemical performance than the linear PANI. After 1300 CV cycles, the CPANI electrode still retained 88.81% of its initial capacitance due to its crosslinking structure.