This is an investigation about the influence of synthesis conditions of graphene oxide (GO) such as KMnO4 concentration and H2SO4/H3PO4 ratio on the structural and electrochemical properties of the Pt/rGO nanocatalyst produced based on gamma irradiation. The catalytic characterizations were evaluated by cyclic voltammetry (CV), impedance spectroscopy (EIS), chronoamperometry (CA), XRD, TEM, FTIR, and Raman. The Pt/rGO for 0.01 g/ml of KMNO4 (Pt-G0.01 K) exhibited the highest stability and anodic peak of current with values of 0.1150 and 17.5 mA/cm2 in terms of methanol oxidation and this value decreased with increasing it. Electrochemical activities enhanced with an increase in acid ratio of 0.07 mA/cm2 for Pt-G50 to 6.46 mA/cm2 for Pt-G100. TEM images showed that the ratio of H2SO4/H3PO4 was effective on the size and concentration of KMnO4 on the amount of produced nanoparticles. The structural defects of Pt-G100 were less than those of the other similar catalysts. Finally, the study proved that manipulation of synthesis parameters of support can significantly change the structural and electrochemical properties of the Pt/rGO nanocatalyst in the radiation technique.