In this work, novel potassium methyl siliconate (PMS) was employed as a new nano-type antioxidant for acrylonitrile-butadiene rubber (NBR). NBR/PMS composites were produced by incorporating various contents of the prepared compound as anti-ageing agents (PMS) to improve the heat resistance of these composites. Potassium methyl siliconate (PMS) was prepared, and its chemical structure was confirmed by different elemental analyses. The curing properties, filler dispersion, thermo-oxidative ageing test, mechanical properties, FTIR, and TGA of the NBR/PMS composites were evaluated. It was detected by TEM images of PMS. The particles had a rhombic shape, and the particle size ranged from 1.23 nm to 7.84 nm. PMS could successfully promote the interfacial interaction between rubber and filler and the uniform dispersion of silica particles into the NBR matrix. As a result, the mechanical characteristics of the NBR/PMS composites were significantly improved, and they were superior to those of the NBR/TMQ composites with similar filler contents. Furthermore, the crosslinking density of the NBR composites was reduced after adding PMS (an antioxidant), which had a great effect on the mechanical properties. The results exhibited that PMS dramatically enhanced the solvent extraction resistance and the thermo-oxidative ageing resistance of NBR/silica composites more efficiently than TMQ. Overall, this work extended the application scope of PMS to develop novel and effective antioxidants for elastomers.