Natural rubber (NR) nanocomposites were prepared by filling cornmeal graphene (CGE) to improve its mechanical properties and thermal properties, and CGE was modified with coupling agents to improve its dispersion in NR. The mechanical properties, wear resistance, thermal stability, and morphology of CGE/NR nanocomposites were studied. The results showed that when NR was 100 phr (parts per hundred rubbers), the CGE was 0.02 phr, and the coupling agent KH590 was 2 phr, the thermal stability and mechanical properties of the CGE/NR nanocomposites were the best. Compared with NR, the thermal conductivity of the nanocomposites increased by 6.0 mW/g, and the decomposition temperature increased by 37 °C. The mechanical properties and wear resistance of KH590-CGE/NR nanocomposites were the best, and compared with NR, the tensile strength, elongation at break, and wear resistance of KH590-CGE/NR nanocomposites increased by 16, 14, and 17%, respectively. The compatibility and dispersion of KH590-CGE/NR nanocomposites were the best.