g-C3N4/CNT as non-platinum catalysts was thermally synthesized for ORR catalyst. The key properties of CNT for electrochemical devices are good electrical conductivity and large surface area with high porosity. ORR onset potentials of g-C3N4 and g-C3N4/CNT catalysts were approximately 0.64 V (NHE) and current density was 4.5 mA/cm2. As increasing the thermal treatment up to 600℃ the catalytic activity was strikingly improved.