In this study, biomimetic Mg-N4-Cx from natural leaves mixed with carbon black (L/C catalyst) exhibits good catalytic activity for oxygen reduction reaction (ORR). The microwave-assisted process offers a cheaper and faster way to synthesize the catalyst compared to the conventional furnace process. Moreover, the microwave assisted process can also avoid the decomposition of porphyrin structure. When the microwave power and treatment time were set to 700 W and 2 min, the L/C catalyst exhibited an electron transfer number of 3.90 and the HO2- yield of only 5 % at 0.25 V vs. RHE, which exceeded other treatment conditions. The Raman spectra denoted that the IG/ID ratio of the L/C catalyst that was obtained using 700 W for 2 min is higher compared to catalyst that used other treatments. Lastly, the L/C catalyst that was obtained using 700 W for 2 min contained high proportion of quaternary-type nitrogen and Mg-N4-Cx. Due to these properties, the catalyst offered good performance and superior long-term stability up to 20000 s.