To explore the effect of potassium perchlorate (KClO4) on Al nanoparticles/MnO2-nanorods nanothermite systems, in this paper, Al/MnO2 nanothermites with different mass fraction of KClO4 were prepared by electrospray. The samples were characterized by XRD, SEM, TG-DSC analysis. According to the results of TG-DSC, the addition of KClO4 seemed to cause no direct improvement on their exothermic reactions. But the results of activation energy calculations showed that KClO4 could remarkably reduce the activation energy of nanothermite systems by up to 48.8%. The XRD results indicated that residues consisted mainly of Mn3O4. The reasons why KClO4 has little effect on thermal properties but makes a great difference on kinetics were analyzed and discussed. Finally, onset combustion tests were carried out. The results and findings provide a useful approach to decrease the activation energy and combustion rate of nanothermites, which may facilitate practical and combustible applications.