Zinc oxide (ZnO) and Calcium carbonate (CaCO3) are the common additives for natural rubber (NR) foams. Nano-ZnO or nano-CaCO3 has smaller particle size and larger specific surface area, more and more attention has been paid to their application in rubber materials in recent years. In this paper, these nanoparticles are applied in NR foam compounds comparing with micron-scaled particles. The effect of nano-particles on the foaming performance, the curing characteristics and properties of NR foams were discus...